--- /dev/null
+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Git User's Manual</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a name="id232381"></a>Git User's Manual</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="preface"><a href="#id264754">Preface</a></span></dt><dt><span class="chapter"><a href="#id233103">1. Git Quick Start</a></span></dt><dd><dl><dt><span class="section"><a href="#id233114">Creating a new repository</a></span></dt><dt><span class="section"><a href="#id233145">Managing branches</a></span></dt><dt><span class="section"><a href="#id232598">Exploring history</a></span></dt><dt><span class="section"><a href="#id232642">Making changes</a></span></dt><dt><span class="section"><a href="#id233404">Merging</a></span></dt><dt><span class="section"><a href="#id233420">Sharing your changes</a></span></dt><dt><span class="section"><a href="#id233504">Repository maintenance</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id232726">2. Repositories and Branches</a></span></dt><dd><dl><dt><span class="section"><a href="#id232732">How to get a git repository</a></span></dt><dt><span class="section"><a href="#id232788">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#id273450">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#id273500">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#id273540">Undestanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#id273568">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#id232302">Manipulating branches</a></span></dt><dt><span class="section"><a href="#id273792">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-with-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#id274036">Fetching branches from other repositories</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id274111">3. Exploring git history</a></span></dt><dd><dl><dt><span class="section"><a href="#id274133">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#id274253">Naming commits</a></span></dt><dt><span class="section"><a href="#id274503">Creating tags</a></span></dt><dt><span class="section"><a href="#id274539">Browsing revisions</a></span></dt><dt><span class="section"><a href="#id274612">Generating diffs</a></span></dt><dt><span class="section"><a href="#id274655">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#id274682">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#id274687">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#id274740">Find first tagged version including a given fix</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id274904">4. Developing with git</a></span></dt><dd><dl><dt><span class="section"><a href="#id274909">Telling git your name</a></span></dt><dt><span class="section"><a href="#id274941">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">how to make a commit</a></span></dt><dt><span class="section"><a href="#id275168">creating good commit messages</a></span></dt><dt><span class="section"><a href="#id275184">how to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dt><span class="section"><a href="#undoing-a-merge">undoing a merge</a></span></dt><dt><span class="section"><a href="#id275420">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#id275449">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#id275502">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#id275560">Fixing a mistake by editing history</a></span></dt><dt><span class="section"><a href="#id275631">Checking out an old version of a file</a></span></dt></dl></dd><dt><span class="section"><a href="#id275689">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#id275727">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#id275732">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#id275807">Recovering lost changes</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id275958">5. Sharing development with others</a></span></dt><dd><dl><dt><span class="section"><a href="#getting-updates-with-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#id276090">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#id276139">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via http</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a git repository via the git protocol</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#id276551">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#id276570">Allow web browsing of a repository</a></span></dt><dt><span class="section"><a href="#id276583">Examples</a></span></dt></dl></dd><dt><span class="chapter"><a href="#cleaning-up-history">6. Rewriting history and maintaining patch series</a></span></dt><dd><dl><dt><span class="section"><a href="#id276614">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#id276689">Keeping a patch series up to date using git-rebase</a></span></dt><dt><span class="section"><a href="#id276826">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#id276886">Other tools</a></span></dt><dt><span class="section"><a href="#id276898">Problems with rewriting history</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id276970">7. Advanced branch management</a></span></dt><dd><dl><dt><span class="section"><a href="#id276976">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fast-forwards">Understanding git history: fast-forwards</a></span></dt><dt><span class="section"><a href="#id277096">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#id277123">Configuring remote branches</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id277247">8. Git internals</a></span></dt><dd><dl><dt><span class="section"><a href="#id277258">The Object Database</a></span></dt><dt><span class="section"><a href="#id277374">Blob Object</a></span></dt><dt><span class="section"><a href="#id277417">Tree Object</a></span></dt><dt><span class="section"><a href="#id277495">Commit Object</a></span></dt><dt><span class="section"><a href="#id277541">Trust</a></span></dt><dt><span class="section"><a href="#id277592">Tag Object</a></span></dt><dt><span class="section"><a href="#id277638">The "index" aka "Current Directory Cache"</a></span></dt><dt><span class="section"><a href="#id277713">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#id277732">working directory -> index</a></span></dt><dt><span class="section"><a href="#id277821">index -> object database</a></span></dt><dt><span class="section"><a href="#id277850">object database -> index</a></span></dt><dt><span class="section"><a href="#id277880">index -> working directory</a></span></dt><dt><span class="section"><a href="#id277944">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#id278039">Examining the data</a></span></dt><dt><span class="section"><a href="#id278117">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#id278204">Merging multiple trees, continued</a></span></dt><dt><span class="section"><a href="#id278464">How git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id278724">9. Glossary of git terms</a></span></dt><dt><span class="chapter"><a href="#id279940">10. Notes and todo list for this manual</a></span></dt></dl></div><div class="preface" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id264754"></a>Preface</h2></div></div></div><p>This manual is designed to be readable by someone with basic unix
+commandline skills, but no previous knowledge of git.</p><p>Chapter 1 gives a brief overview of git commands, without any
+explanation; you may prefer to skip to chapter 2 on a first reading.</p><p>Chapters 2 and 3 explain how to fetch and study a project using
+git—the tools you'd need to build and test a particular version of a
+software project, to search for regressions, and so on.</p><p>Chapter 4 explains how to do development with git, and chapter 5 how
+to share that development with others.</p><p>Further chapters cover more specialized topics.</p><p>Comprehensive reference documentation is available through the man
+pages. For a command such as "git clone", just use</p><div class="literallayout"><p>$ man git-clone</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id233103"></a>Chapter 1. Git Quick Start</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id233114">Creating a new repository</a></span></dt><dt><span class="section"><a href="#id233145">Managing branches</a></span></dt><dt><span class="section"><a href="#id232598">Exploring history</a></span></dt><dt><span class="section"><a href="#id232642">Making changes</a></span></dt><dt><span class="section"><a href="#id233404">Merging</a></span></dt><dt><span class="section"><a href="#id233420">Sharing your changes</a></span></dt><dt><span class="section"><a href="#id233504">Repository maintenance</a></span></dt></dl></div><p>This is a quick summary of the major commands; the following chapters
+will explain how these work in more detail.</p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id233114"></a>Creating a new repository</h2></div></div></div><p>From a tarball:</p><div class="literallayout"><p>$ tar xzf project.tar.gz<br>
+$ cd project<br>
+$ git init<br>
+Initialized empty Git repository in .git/<br>
+$ git add .<br>
+$ git commit</p></div><p>From a remote repository:</p><div class="literallayout"><p>$ git clone git://example.com/pub/project.git<br>
+$ cd project</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id233145"></a>Managing branches</h2></div></div></div><div class="literallayout"><p>$ git branch # list all branches in this repo<br>
+$ git checkout test # switch working directory to branch "test"<br>
+$ git branch new # create branch "new" starting at current HEAD<br>
+$ git branch -d new # delete branch "new"</p></div><p>Instead of basing new branch on current HEAD (the default), use:</p><div class="literallayout"><p>$ git branch new test # branch named "test"<br>
+$ git branch new v2.6.15 # tag named v2.6.15<br>
+$ git branch new HEAD^ # commit before the most recent<br>
+$ git branch new HEAD^^ # commit before that<br>
+$ git branch new test~10 # ten commits before tip of branch "test"</p></div><p>Create and switch to a new branch at the same time:</p><div class="literallayout"><p>$ git checkout -b new v2.6.15</p></div><p>Update and examine branches from the repository you cloned from:</p><div class="literallayout"><p>$ git fetch # update<br>
+$ git branch -r # list<br>
+ origin/master<br>
+ origin/next<br>
+ ...<br>
+$ git branch checkout -b masterwork origin/master</p></div><p>Fetch a branch from a different repository, and give it a new
+name in your repository:</p><div class="literallayout"><p>$ git fetch git://example.com/project.git theirbranch:mybranch<br>
+$ git fetch git://example.com/project.git v2.6.15:mybranch</p></div><p>Keep a list of repositories you work with regularly:</p><div class="literallayout"><p>$ git remote add example git://example.com/project.git<br>
+$ git remote # list remote repositories<br>
+example<br>
+origin<br>
+$ git remote show example # get details<br>
+* remote example<br>
+ URL: git://example.com/project.git<br>
+ Tracked remote branches<br>
+ master next ...<br>
+$ git fetch example # update branches from example<br>
+$ git branch -r # list all remote branches</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id232598"></a>Exploring history</h2></div></div></div><div class="literallayout"><p>$ gitk # visualize and browse history<br>
+$ git log # list all commits<br>
+$ git log src/ # ...modifying src/<br>
+$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15<br>
+$ git log master..test # ...in branch test, not in branch master<br>
+$ git log test..master # ...in branch master, but not in test<br>
+$ git log test...master # ...in one branch, not in both<br>
+$ git log -S'foo()' # ...where difference contain "foo()"<br>
+$ git log --since="2 weeks ago"<br>
+$ git log -p # show patches as well<br>
+$ git show # most recent commit<br>
+$ git diff v2.6.15..v2.6.16 # diff between two tagged versions<br>
+$ git diff v2.6.15..HEAD # diff with current head<br>
+$ git grep "foo()" # search working directory for "foo()"<br>
+$ git grep v2.6.15 "foo()" # search old tree for "foo()"<br>
+$ git show v2.6.15:a.txt # look at old version of a.txt</p></div><p>Search for regressions:</p><div class="literallayout"><p>$ git bisect start<br>
+$ git bisect bad # current version is bad<br>
+$ git bisect good v2.6.13-rc2 # last known good revision<br>
+Bisecting: 675 revisions left to test after this<br>
+ # test here, then:<br>
+$ git bisect good # if this revision is good, or<br>
+$ git bisect bad # if this revision is bad.<br>
+ # repeat until done.</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id232642"></a>Making changes</h2></div></div></div><p>Make sure git knows who to blame:</p><div class="literallayout"><p>$ cat >~/.gitconfig <<\EOF<br>
+[user]<br>
+name = Your Name Comes Here<br>
+email = you@yourdomain.example.com<br>
+EOF</p></div><p>Select file contents to include in the next commit, then make the
+commit:</p><div class="literallayout"><p>$ git add a.txt # updated file<br>
+$ git add b.txt # new file<br>
+$ git rm c.txt # old file<br>
+$ git commit</p></div><p>Or, prepare and create the commit in one step:</p><div class="literallayout"><p>$ git commit d.txt # use latest content only of d.txt<br>
+$ git commit -a # use latest content of all tracked files</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id233404"></a>Merging</h2></div></div></div><div class="literallayout"><p>$ git merge test # merge branch "test" into the current branch<br>
+$ git pull git://example.com/project.git master<br>
+ # fetch and merge in remote branch<br>
+$ git pull . test # equivalent to git merge test</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id233420"></a>Sharing your changes</h2></div></div></div><p>Importing or exporting patches:</p><div class="literallayout"><p>$ git format-patch origin..HEAD # format a patch for each commit<br>
+ # in HEAD but not in origin<br>
+$ git-am mbox # import patches from the mailbox "mbox"</p></div><p>Fetch a branch in a different git repository, then merge into the
+current branch:</p><div class="literallayout"><p>$ git pull git://example.com/project.git theirbranch</p></div><p>Store the fetched branch into a local branch before merging into the
+current branch:</p><div class="literallayout"><p>$ git pull git://example.com/project.git theirbranch:mybranch</p></div><p>After creating commits on a local branch, update the remote
+branch with your commits:</p><div class="literallayout"><p>$ git push ssh://example.com/project.git mybranch:theirbranch</p></div><p>When remote and local branch are both named "test":</p><div class="literallayout"><p>$ git push ssh://example.com/project.git test</p></div><p>Shortcut version for a frequently used remote repository:</p><div class="literallayout"><p>$ git remote add example ssh://example.com/project.git<br>
+$ git push example test</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id233504"></a>Repository maintenance</h2></div></div></div><p>Check for corruption:</p><div class="literallayout"><p>$ git fsck</p></div><p>Recompress, remove unused cruft:</p><div class="literallayout"><p>$ git gc</p></div></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id232726"></a>Chapter 2. Repositories and Branches</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id232732">How to get a git repository</a></span></dt><dt><span class="section"><a href="#id232788">How to check out a different version of a project</a></span></dt><dt><span class="section"><a href="#id273450">Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#id273500">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#id273540">Undestanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#id273568">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="section"><a href="#id232302">Manipulating branches</a></span></dt><dt><span class="section"><a href="#id273792">Examining branches from a remote repository</a></span></dt><dt><span class="section"><a href="#how-git-stores-references">Naming branches, tags, and other references</a></span></dt><dt><span class="section"><a href="#Updating-a-repository-with-git-fetch">Updating a repository with git fetch</a></span></dt><dt><span class="section"><a href="#id274036">Fetching branches from other repositories</a></span></dt></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id232732"></a>How to get a git repository</h2></div></div></div><p>It will be useful to have a git repository to experiment with as you
+read this manual.</p><p>The best way to get one is by using the <a href="git-clone.html" target="_top">git-clone(1)</a> command
+to download a copy of an existing repository for a project that you
+are interested in. If you don't already have a project in mind, here
+are some interesting examples:</p><div class="literallayout"><p> # git itself (approx. 10MB download):<br>
+$ git clone git://git.kernel.org/pub/scm/git/git.git<br>
+ # the linux kernel (approx. 150MB download):<br>
+$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git</p></div><p>The initial clone may be time-consuming for a large project, but you
+will only need to clone once.</p><p>The clone command creates a new directory named after the project
+("git" or "linux-2.6" in the examples above). After you cd into this
+directory, you will see that it contains a copy of the project files,
+together with a special top-level directory named ".git", which
+contains all the information about the history of the project.</p><p>In most of the following, examples will be taken from one of the two
+repositories above.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id232788"></a>How to check out a different version of a project</h2></div></div></div><p>Git is best thought of as a tool for storing the history of a
+collection of files. It stores the history as a compressed
+collection of interrelated snapshots (versions) of the project's
+contents.</p><p>A single git repository may contain multiple branches. Each branch
+is a bookmark referencing a particular point in the project history.
+The <a href="git-branch.html" target="_top">git-branch(1)</a> command shows you the list of branches:</p><div class="literallayout"><p>$ git branch<br>
+* master</p></div><p>A freshly cloned repository contains a single branch, named "master",
+and the working directory contains the version of the project
+referred to by the master branch.</p><p>Most projects also use tags. Tags, like branches, are references
+into the project's history, and can be listed using the
+<a href="git-tag.html" target="_top">git-tag(1)</a> command:</p><div class="literallayout"><p>$ git tag -l<br>
+v2.6.11<br>
+v2.6.11-tree<br>
+v2.6.12<br>
+v2.6.12-rc2<br>
+v2.6.12-rc3<br>
+v2.6.12-rc4<br>
+v2.6.12-rc5<br>
+v2.6.12-rc6<br>
+v2.6.13<br>
+...</p></div><p>Tags are expected to always point at the same version of a project,
+while branches are expected to advance as development progresses.</p><p>Create a new branch pointing to one of these versions and check it
+out using <a href="git-checkout.html" target="_top">git-checkout(1)</a>:</p><div class="literallayout"><p>$ git checkout -b new v2.6.13</p></div><p>The working directory then reflects the contents that the project had
+when it was tagged v2.6.13, and <a href="git-branch.html" target="_top">git-branch(1)</a> shows two
+branches, with an asterisk marking the currently checked-out branch:</p><div class="literallayout"><p>$ git branch<br>
+ master<br>
+* new</p></div><p>If you decide that you'd rather see version 2.6.17, you can modify
+the current branch to point at v2.6.17 instead, with</p><div class="literallayout"><p>$ git reset --hard v2.6.17</p></div><p>Note that if the current branch was your only reference to a
+particular point in history, then resetting that branch may leave you
+with no way to find the history it used to point to; so use this
+command carefully.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id273450"></a>Understanding History: Commits</h2></div></div></div><p>Every change in the history of a project is represented by a commit.
+The <a href="git-show.html" target="_top">git-show(1)</a> command shows the most recent commit on the
+current branch:</p><div class="literallayout"><p>$ git show<br>
+commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2<br>
+Author: Jamal Hadi Salim <hadi@cyberus.ca><br>
+Date: Sat Dec 2 22:22:25 2006 -0800<br>
+<br>
+ [XFRM]: Fix aevent structuring to be more complete.<br>
+<br>
+ aevents can not uniquely identify an SA. We break the ABI with this<br>
+ patch, but consensus is that since it is not yet utilized by any<br>
+ (known) application then it is fine (better do it now than later).<br>
+<br>
+ Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca><br>
+ Signed-off-by: David S. Miller <davem@davemloft.net><br>
+<br>
+diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt<br>
+index 8be626f..d7aac9d 100644<br>
+--- a/Documentation/networking/xfrm_sync.txt<br>
++++ b/Documentation/networking/xfrm_sync.txt<br>
+@@ -47,10 +47,13 @@ aevent_id structure looks like:<br>
+<br>
+ struct xfrm_aevent_id {<br>
+ struct xfrm_usersa_id sa_id;<br>
++ xfrm_address_t saddr;<br>
+ __u32 flags;<br>
++ __u32 reqid;<br>
+ };<br>
+...</p></div><p>As you can see, a commit shows who made the latest change, what they
+did, and why.</p><p>Every commit has a 40-hexdigit id, sometimes called the "object name"
+or the "SHA1 id", shown on the first line of the "git show" output.
+You can usually refer to a commit by a shorter name, such as a tag or a
+branch name, but this longer name can also be useful. Most
+importantly, it is a globally unique name for this commit: so if you
+tell somebody else the object name (for example in email), then you are
+guaranteed that name will refer to the same commit in their repository
+that you it does in yours (assuming their repository has that commit at
+all).</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id273500"></a>Understanding history: commits, parents, and reachability</h3></div></div></div><p>Every commit (except the very first commit in a project) also has a
+parent commit which shows what happened before this commit.
+Following the chain of parents will eventually take you back to the
+beginning of the project.</p><p>However, the commits do not form a simple list; git allows lines of
+development to diverge and then reconverge, and the point where two
+lines of development reconverge is called a "merge". The commit
+representing a merge can therefore have more than one parent, with
+each parent representing the most recent commit on one of the lines
+of development leading to that point.</p><p>The best way to see how this works is using the <a href="gitk.html" target="_top">gitk(1)</a>
+command; running gitk now on a git repository and looking for merge
+commits will help understand how the git organizes history.</p><p>In the following, we say that commit X is "reachable" from commit Y
+if commit X is an ancestor of commit Y. Equivalently, you could say
+that Y is a descendent of X, or that there is a chain of parents
+leading from commit Y to commit X.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id273540"></a>Undestanding history: History diagrams</h3></div></div></div><p>We will sometimes represent git history using diagrams like the one
+below. Commits are shown as "o", and the links between them with
+lines drawn with - / and \. Time goes left to right:</p><pre class="literallayout"> o--o--o <-- Branch A
+ /
+o--o--o <-- master
+ o--o--o <-- Branch B</pre><p>If we need to talk about a particular commit, the character "o" may
+be replaced with another letter or number.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id273568"></a>Understanding history: What is a branch?</h3></div></div></div><p>Though we've been using the word "branch" to mean a kind of reference
+to a particular commit, the word branch is also commonly used to
+refer to the line of commits leading up to that point. In the
+example above, git may think of the branch named "A" as just a
+pointer to one particular commit, but we may refer informally to the
+line of three commits leading up to that point as all being part of
+"branch A".</p><p>If we need to make it clear that we're just talking about the most
+recent commit on the branch, we may refer to that commit as the
+"head" of the branch.</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id232302"></a>Manipulating branches</h2></div></div></div><p>Creating, deleting, and modifying branches is quick and easy; here's
+a summary of the commands:</p><div class="variablelist"><dl><dt><span class="term">
+git branch
+</span></dt><dd>
+ list all branches
+</dd><dt><span class="term">
+git branch <branch>
+</span></dt><dd>
+ create a new branch named <branch>, referencing the same
+ point in history as the current branch
+</dd><dt><span class="term">
+git branch <branch> <start-point>
+</span></dt><dd>
+ create a new branch named <branch>, referencing
+ <start-point>, which may be specified any way you like,
+ including using a branch name or a tag name
+</dd><dt><span class="term">
+git branch -d <branch>
+</span></dt><dd>
+ delete the branch <branch>; if the branch you are deleting
+ points to a commit which is not reachable from this branch,
+ this command will fail with a warning.
+</dd><dt><span class="term">
+git branch -D <branch>
+</span></dt><dd>
+ even if the branch points to a commit not reachable
+ from the current branch, you may know that that commit
+ is still reachable from some other branch or tag. In that
+ case it is safe to use this command to force git to delete
+ the branch.
+</dd><dt><span class="term">
+git checkout <branch>
+</span></dt><dd>
+ make the current branch <branch>, updating the working
+ directory to reflect the version referenced by <branch>
+</dd><dt><span class="term">
+git checkout -b <new> <start-point>
+</span></dt><dd>
+ create a new branch <new> referencing <start-point>, and
+ check it out.
+</dd></dl></div><p>It is also useful to know that the special symbol "HEAD" can always
+be used to refer to the current branch.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id273792"></a>Examining branches from a remote repository</h2></div></div></div><p>The "master" branch that was created at the time you cloned is a copy
+of the HEAD in the repository that you cloned from. That repository
+may also have had other branches, though, and your local repository
+keeps branches which track each of those remote branches, which you
+can view using the "-r" option to <a href="git-branch.html" target="_top">git-branch(1)</a>:</p><div class="literallayout"><p>$ git branch -r<br>
+ origin/HEAD<br>
+ origin/html<br>
+ origin/maint<br>
+ origin/man<br>
+ origin/master<br>
+ origin/next<br>
+ origin/pu<br>
+ origin/todo</p></div><p>You cannot check out these remote-tracking branches, but you can
+examine them on a branch of your own, just as you would a tag:</p><div class="literallayout"><p>$ git checkout -b my-todo-copy origin/todo</p></div><p>Note that the name "origin" is just the name that git uses by default
+to refer to the repository that you cloned from.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-git-stores-references"></a>Naming branches, tags, and other references</h2></div></div></div><p>Branches, remote-tracking branches, and tags are all references to
+commits. All references are named with a slash-separated path name
+starting with "refs"; the names we've been using so far are actually
+shorthand:</p><div class="itemizedlist"><ul type="disc"><li>
+The branch "test" is short for "refs/heads/test".
+</li><li>
+The tag "v2.6.18" is short for "refs/tags/v2.6.18".
+</li><li>
+"origin/master" is short for "refs/remotes/origin/master".
+</li></ul></div><p>The full name is occasionally useful if, for example, there ever
+exists a tag and a branch with the same name.</p><p>As another useful shortcut, if the repository "origin" posesses only
+a single branch, you can refer to that branch as just "origin".</p><p>More generally, if you have defined a remote repository named
+"example", you can refer to the branch in that repository as
+"example". And for a repository with multiple branches, this will
+refer to the branch designated as the "HEAD" branch.</p><p>For the complete list of paths which git checks for references, and
+the order it uses to decide which to choose when there are multiple
+references with the same shorthand name, see the "SPECIFYING
+REVISIONS" section of <a href="git-rev-parse.html" target="_top">git-rev-parse(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="Updating-a-repository-with-git-fetch"></a>Updating a repository with git fetch</h2></div></div></div><p>Eventually the developer cloned from will do additional work in her
+repository, creating new commits and advancing the branches to point
+at the new commits.</p><p>The command "git fetch", with no arguments, will update all of the
+remote-tracking branches to the latest version found in her
+repository. It will not touch any of your own branches—not even the
+"master" branch that was created for you on clone.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274036"></a>Fetching branches from other repositories</h2></div></div></div><p>You can also track branches from repositories other than the one you
+cloned from, using <a href="git-remote.html" target="_top">git-remote(1)</a>:</p><div class="literallayout"><p>$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git<br>
+$ git fetch<br>
+* refs/remotes/linux-nfs/master: storing branch 'master' ...<br>
+ commit: bf81b46</p></div><p>New remote-tracking branches will be stored under the shorthand name
+that you gave "git remote add", in this case linux-nfs:</p><div class="literallayout"><p>$ git branch -r<br>
+linux-nfs/master<br>
+origin/master</p></div><p>If you run "git fetch <remote>" later, the tracking branches for the
+named <remote> will be updated.</p><p>If you examine the file .git/config, you will see that git has added
+a new stanza:</p><div class="literallayout"><p>$ cat .git/config<br>
+...<br>
+[remote "linux-nfs"]<br>
+ url = git://linux-nfs.org/~bfields/git.git<br>
+ fetch = +refs/heads/*:refs/remotes/linux-nfs-read/*<br>
+...</p></div><p>This is what causes git to track the remote's branches; you may modify
+or delete these configuration options by editing .git/config with a
+text editor. (See the "CONFIGURATION FILE" section of
+<a href="git-config.html" target="_top">git-config(1)</a> for details.)</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id274111"></a>Chapter 3. Exploring git history</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id274133">How to use bisect to find a regression</a></span></dt><dt><span class="section"><a href="#id274253">Naming commits</a></span></dt><dt><span class="section"><a href="#id274503">Creating tags</a></span></dt><dt><span class="section"><a href="#id274539">Browsing revisions</a></span></dt><dt><span class="section"><a href="#id274612">Generating diffs</a></span></dt><dt><span class="section"><a href="#id274655">Viewing old file versions</a></span></dt><dt><span class="section"><a href="#id274682">Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#id274687">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#id274740">Find first tagged version including a given fix</a></span></dt></dl></dd></dl></div><p>Git is best thought of as a tool for storing the history of a
+collection of files. It does this by storing compressed snapshots of
+the contents of a file heirarchy, together with "commits" which show
+the relationships between these snapshots.</p><p>Git provides extremely flexible and fast tools for exploring the
+history of a project.</p><p>We start with one specialized tool which is useful for finding the
+commit that introduced a bug into a project.</p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274133"></a>How to use bisect to find a regression</h2></div></div></div><p>Suppose version 2.6.18 of your project worked, but the version at
+"master" crashes. Sometimes the best way to find the cause of such a
+regression is to perform a brute-force search through the project's
+history to find the particular commit that caused the problem. The
+<a href="git-bisect.html" target="_top">git-bisect(1)</a> command can help you do this:</p><div class="literallayout"><p>$ git bisect start<br>
+$ git bisect good v2.6.18<br>
+$ git bisect bad master<br>
+Bisecting: 3537 revisions left to test after this<br>
+[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]</p></div><p>If you run "git branch" at this point, you'll see that git has
+temporarily moved you to a new branch named "bisect". This branch
+points to a commit (with commit id 65934…) that is reachable from
+v2.6.19 but not from v2.6.18. Compile and test it, and see whether
+it crashes. Assume it does crash. Then:</p><div class="literallayout"><p>$ git bisect bad<br>
+Bisecting: 1769 revisions left to test after this<br>
+[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings</p></div><p>checks out an older version. Continue like this, telling git at each
+stage whether the version it gives you is good or bad, and notice
+that the number of revisions left to test is cut approximately in
+half each time.</p><p>After about 13 tests (in this case), it will output the commit id of
+the guilty commit. You can then examine the commit with
+<a href="git-show.html" target="_top">git-show(1)</a>, find out who wrote it, and mail them your bug
+report with the commit id. Finally, run</p><div class="literallayout"><p>$ git bisect reset</p></div><p>to return you to the branch you were on before and delete the
+temporary "bisect" branch.</p><p>Note that the version which git-bisect checks out for you at each
+point is just a suggestion, and you're free to try a different
+version if you think it would be a good idea. For example,
+occasionally you may land on a commit that broke something unrelated;
+run</p><div class="literallayout"><p>$ git bisect-visualize</p></div><p>which will run gitk and label the commit it chose with a marker that
+says "bisect". Chose a safe-looking commit nearby, note its commit
+id, and check it out with:</p><div class="literallayout"><p>$ git reset --hard fb47ddb2db...</p></div><p>then test, run "bisect good" or "bisect bad" as appropriate, and
+continue.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274253"></a>Naming commits</h2></div></div></div><p>We have seen several ways of naming commits already:</p><div class="itemizedlist"><ul type="disc"><li>
+40-hexdigit object name
+</li><li>
+branch name: refers to the commit at the head of the given
+ branch
+</li><li>
+tag name: refers to the commit pointed to by the given tag
+ (we've seen branches and tags are special cases of
+ <a href="#how-git-stores-references" title="Naming branches, tags, and other references">references</a>).
+</li><li>
+HEAD: refers to the head of the current branch
+</li></ul></div><p>There are many more; see the "SPECIFYING REVISIONS" section of the
+<a href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> man page for the complete list of ways to
+name revisions. Some examples:</p><div class="literallayout"><p>$ git show fb47ddb2 # the first few characters of the object name<br>
+ # are usually enough to specify it uniquely<br>
+$ git show HEAD^ # the parent of the HEAD commit<br>
+$ git show HEAD^^ # the grandparent<br>
+$ git show HEAD~4 # the great-great-grandparent</p></div><p>Recall that merge commits may have more than one parent; by default,
+^ and ~ follow the first parent listed in the commit, but you can
+also choose:</p><div class="literallayout"><p>$ git show HEAD^1 # show the first parent of HEAD<br>
+$ git show HEAD^2 # show the second parent of HEAD</p></div><p>In addition to HEAD, there are several other special names for
+commits:</p><p>Merges (to be discussed later), as well as operations such as
+git-reset, which change the currently checked-out commit, generally
+set ORIG_HEAD to the value HEAD had before the current operation.</p><p>The git-fetch operation always stores the head of the last fetched
+branch in FETCH_HEAD. For example, if you run git fetch without
+specifying a local branch as the target of the operation</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git theirbranch</p></div><p>the fetched commits will still be available from FETCH_HEAD.</p><p>When we discuss merges we'll also see the special name MERGE_HEAD,
+which refers to the other branch that we're merging in to the current
+branch.</p><p>The <a href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> command is a low-level command that is
+occasionally useful for translating some name for a commit to the object
+name for that commit:</p><div class="literallayout"><p>$ git rev-parse origin<br>
+e05db0fd4f31dde7005f075a84f96b360d05984b</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274503"></a>Creating tags</h2></div></div></div><p>We can also create a tag to refer to a particular commit; after
+running</p><div class="literallayout"><p>$ git-tag stable-1 1b2e1d63ff</p></div><p>You can use stable-1 to refer to the commit 1b2e1d63ff.</p><p>This creates a "lightweight" tag. If the tag is a tag you wish to
+share with others, and possibly sign cryptographically, then you
+should create a tag object instead; see the <a href="git-tag.html" target="_top">git-tag(1)</a> man
+page for details.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274539"></a>Browsing revisions</h2></div></div></div><p>The <a href="git-log.html" target="_top">git-log(1)</a> command can show lists of commits. On its
+own, it shows all commits reachable from the parent commit; but you
+can also make more specific requests:</p><div class="literallayout"><p>$ git log v2.5.. # commits since (not reachable from) v2.5<br>
+$ git log test..master # commits reachable from master but not test<br>
+$ git log master..test # ...reachable from test but not master<br>
+$ git log master...test # ...reachable from either test or master,<br>
+ # but not both<br>
+$ git log --since="2 weeks ago" # commits from the last 2 weeks<br>
+$ git log Makefile # commits which modify Makefile<br>
+$ git log fs/ # ... which modify any file under fs/<br>
+$ git log -S'foo()' # commits which add or remove any file data<br>
+ # matching the string 'foo()'</p></div><p>And of course you can combine all of these; the following finds
+commits since v2.5 which touch the Makefile or any file under fs:</p><div class="literallayout"><p>$ git log v2.5.. Makefile fs/</p></div><p>You can also ask git log to show patches:</p><div class="literallayout"><p>$ git log -p</p></div><p>See the "—pretty" option in the <a href="git-log.html" target="_top">git-log(1)</a> man page for more
+display options.</p><p>Note that git log starts with the most recent commit and works
+backwards through the parents; however, since git history can contain
+multiple independant lines of development, the particular order that
+commits are listed in may be somewhat arbitrary.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274612"></a>Generating diffs</h2></div></div></div><p>You can generate diffs between any two versions using
+<a href="git-diff.html" target="_top">git-diff(1)</a>:</p><div class="literallayout"><p>$ git diff master..test</p></div><p>Sometimes what you want instead is a set of patches:</p><div class="literallayout"><p>$ git format-patch master..test</p></div><p>will generate a file with a patch for each commit reachable from test
+but not from master. Note that if master also has commits which are
+not reachable from test, then the combined result of these patches
+will not be the same as the diff produced by the git-diff example.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274655"></a>Viewing old file versions</h2></div></div></div><p>You can always view an old version of a file by just checking out the
+correct revision first. But sometimes it is more convenient to be
+able to view an old version of a single file without checking
+anything out; this command does that:</p><div class="literallayout"><p>$ git show v2.5:fs/locks.c</p></div><p>Before the colon may be anything that names a commit, and after it
+may be any path to a file tracked by git.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274682"></a>Examples</h2></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id274687"></a>Check whether two branches point at the same history</h3></div></div></div><p>Suppose you want to check whether two branches point at the same point
+in history.</p><div class="literallayout"><p>$ git diff origin..master</p></div><p>will tell you whether the contents of the project are the same at the
+two branches; in theory, however, it's possible that the same project
+contents could have been arrived at by two different historical
+routes. You could compare the object names:</p><div class="literallayout"><p>$ git rev-list origin<br>
+e05db0fd4f31dde7005f075a84f96b360d05984b<br>
+$ git rev-list master<br>
+e05db0fd4f31dde7005f075a84f96b360d05984b</p></div><p>Or you could recall that the … operator selects all commits
+contained reachable from either one reference or the other but not
+both: so</p><div class="literallayout"><p>$ git log origin...master</p></div><p>will return no commits when the two branches are equal.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id274740"></a>Find first tagged version including a given fix</h3></div></div></div><p>Suppose you know that the commit e05db0fd fixed a certain problem.
+You'd like to find the earliest tagged release that contains that
+fix.</p><p>Of course, there may be more than one answer—if the history branched
+after commit e05db0fd, then there could be multiple "earliest" tagged
+releases.</p><p>You could just visually inspect the commits since e05db0fd:</p><div class="literallayout"><p>$ gitk e05db0fd..</p></div><p>Or you can use <a href="git-name-rev.html" target="_top">git-name-rev(1)</a>, which will give the commit a
+name based on any tag it finds pointing to one of the commit's
+descendants:</p><div class="literallayout"><p>$ git name-rev e05db0fd<br>
+e05db0fd tags/v1.5.0-rc1^0~23</p></div><p>The <a href="git-describe.html" target="_top">git-describe(1)</a> command does the opposite, naming the
+revision using a tag on which the given commit is based:</p><div class="literallayout"><p>$ git describe e05db0fd<br>
+v1.5.0-rc0-ge05db0f</p></div><p>but that may sometimes help you guess which tags might come after the
+given commit.</p><p>If you just want to verify whether a given tagged version contains a
+given commit, you could use <a href="git-merge-base.html" target="_top">git-merge-base(1)</a>:</p><div class="literallayout"><p>$ git merge-base e05db0fd v1.5.0-rc1<br>
+e05db0fd4f31dde7005f075a84f96b360d05984b</p></div><p>The merge-base command finds a common ancestor of the given commits,
+and always returns one or the other in the case where one is a
+descendant of the other; so the above output shows that e05db0fd
+actually is an ancestor of v1.5.0-rc1.</p><p>Alternatively, note that</p><div class="literallayout"><p>$ git log v1.5.0-rc1..e05db0fd</p></div><p>will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
+because it outputs only commits that are not reachable from v1.5.0-rc1.</p><p>As yet another alternative, the <a href="git-show-branch.html" target="_top">git-show-branch(1)</a> command lists
+the commits reachable from its arguments with a display on the left-hand
+side that indicates which arguments that commit is reachable from. So,
+you can run something like</p><div class="literallayout"><p>$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2<br>
+! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if<br>
+available<br>
+ ! [v1.5.0-rc0] GIT v1.5.0 preview<br>
+ ! [v1.5.0-rc1] GIT v1.5.0-rc1<br>
+ ! [v1.5.0-rc2] GIT v1.5.0-rc2<br>
+...</p></div><p>then search for a line that looks like</p><div class="literallayout"><p>+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if<br>
+available</p></div><p>Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
+from v1.5.0-rc2, but not from v1.5.0-rc0.</p></div></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id274904"></a>Chapter 4. Developing with git</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id274909">Telling git your name</a></span></dt><dt><span class="section"><a href="#id274941">Creating a new repository</a></span></dt><dt><span class="section"><a href="#how-to-make-a-commit">how to make a commit</a></span></dt><dt><span class="section"><a href="#id275168">creating good commit messages</a></span></dt><dt><span class="section"><a href="#id275184">how to merge</a></span></dt><dt><span class="section"><a href="#resolving-a-merge">Resolving a merge</a></span></dt><dt><span class="section"><a href="#undoing-a-merge">undoing a merge</a></span></dt><dt><span class="section"><a href="#id275420">Fast-forward merges</a></span></dt><dt><span class="section"><a href="#id275449">Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#id275502">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#id275560">Fixing a mistake by editing history</a></span></dt><dt><span class="section"><a href="#id275631">Checking out an old version of a file</a></span></dt></dl></dd><dt><span class="section"><a href="#id275689">Ensuring good performance</a></span></dt><dt><span class="section"><a href="#id275727">Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#id275732">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#id275807">Recovering lost changes</a></span></dt></dl></dd></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274909"></a>Telling git your name</h2></div></div></div><p>Before creating any commits, you should introduce yourself to git. The
+easiest way to do so is:</p><div class="literallayout"><p>$ cat >~/.gitconfig <<\EOF<br>
+[user]<br>
+ name = Your Name Comes Here<br>
+ email = you@yourdomain.example.com<br>
+EOF</p></div><p>(See the "CONFIGURATION FILE" section of <a href="git-config.html" target="_top">git-config(1)</a> for
+details on the configuration file.)</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id274941"></a>Creating a new repository</h2></div></div></div><p>Creating a new repository from scratch is very easy:</p><div class="literallayout"><p>$ mkdir project<br>
+$ cd project<br>
+$ git init</p></div><p>If you have some initial content (say, a tarball):</p><div class="literallayout"><p>$ tar -xzvf project.tar.gz<br>
+$ cd project<br>
+$ git init<br>
+$ git add . # include everything below ./ in the first commit:<br>
+$ git commit</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="how-to-make-a-commit"></a>how to make a commit</h2></div></div></div><p>Creating a new commit takes three steps:</p><div class="orderedlist"><ol type="1"><li>
+Making some changes to the working directory using your
+ favorite editor.
+</li><li>
+Telling git about your changes.
+</li><li>
+Creating the commit using the content you told git about
+ in step 2.
+</li></ol></div><p>In practice, you can interleave and repeat steps 1 and 2 as many
+times as you want: in order to keep track of what you want committed
+at step 3, git maintains a snapshot of the tree's contents in a
+special staging area called "the index."</p><p>At the beginning, the content of the index will be identical to
+that of the HEAD. The command "git diff —cached", which shows
+the difference between the HEAD and the index, should therefore
+produce no output at that point.</p><p>Modifying the index is easy:</p><p>To update the index with the new contents of a modified file, use</p><div class="literallayout"><p>$ git add path/to/file</p></div><p>To add the contents of a new file to the index, use</p><div class="literallayout"><p>$ git add path/to/file</p></div><p>To remove a file from the index and from the working tree,</p><div class="literallayout"><p>$ git rm path/to/file</p></div><p>After each step you can verify that</p><div class="literallayout"><p>$ git diff --cached</p></div><p>always shows the difference between the HEAD and the index file—this
+is what you'd commit if you created the commit now—and that</p><div class="literallayout"><p>$ git diff</p></div><p>shows the difference between the working tree and the index file.</p><p>Note that "git add" always adds just the current contents of a file
+to the index; further changes to the same file will be ignored unless
+you run git-add on the file again.</p><p>When you're ready, just run</p><div class="literallayout"><p>$ git commit</p></div><p>and git will prompt you for a commit message and then create the new
+commmit. Check to make sure it looks like what you expected with</p><div class="literallayout"><p>$ git show</p></div><p>As a special shortcut,</p><div class="literallayout"><p>$ git commit -a</p></div><p>will update the index with any files that you've modified or removed
+and create a commit, all in one step.</p><p>A number of commands are useful for keeping track of what you're
+about to commit:</p><div class="literallayout"><p>$ git diff --cached # difference between HEAD and the index; what<br>
+ # would be commited if you ran "commit" now.<br>
+$ git diff # difference between the index file and your<br>
+ # working directory; changes that would not<br>
+ # be included if you ran "commit" now.<br>
+$ git status # a brief per-file summary of the above.</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275168"></a>creating good commit messages</h2></div></div></div><p>Though not required, it's a good idea to begin the commit message
+with a single short (less than 50 character) line summarizing the
+change, followed by a blank line and then a more thorough
+description. Tools that turn commits into email, for example, use
+the first line on the Subject line and the rest of the commit in the
+body.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275184"></a>how to merge</h2></div></div></div><p>You can rejoin two diverging branches of development using
+<a href="git-merge.html" target="_top">git-merge(1)</a>:</p><div class="literallayout"><p>$ git merge branchname</p></div><p>merges the development in the branch "branchname" into the current
+branch. If there are conflicts—for example, if the same file is
+modified in two different ways in the remote branch and the local
+branch—then you are warned; the output may look something like this:</p><div class="literallayout"><p>$ git pull . next<br>
+Trying really trivial in-index merge...<br>
+fatal: Merge requires file-level merging<br>
+Nope.<br>
+Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086<br>
+Merging:<br>
+15e2162 world<br>
+77976da goodbye<br>
+found 1 common ancestor(s):<br>
+d122ed4 initial<br>
+Auto-merging file.txt<br>
+CONFLICT (content): Merge conflict in file.txt<br>
+Automatic merge failed; fix conflicts and then commit the result.</p></div><p>Conflict markers are left in the problematic files, and after
+you resolve the conflicts manually, you can update the index
+with the contents and run git commit, as you normally would when
+creating a new file.</p><p>If you examine the resulting commit using gitk, you will see that it
+has two parents, one pointing to the top of the current branch, and
+one to the top of the other branch.</p><p>In more detail:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="resolving-a-merge"></a>Resolving a merge</h2></div></div></div><p>When a merge isn't resolved automatically, git leaves the index and
+the working tree in a special state that gives you all the
+information you need to help resolve the merge.</p><p>Files with conflicts are marked specially in the index, so until you
+resolve the problem and update the index, git commit will fail:</p><div class="literallayout"><p>$ git commit<br>
+file.txt: needs merge</p></div><p>Also, git status will list those files as "unmerged".</p><p>All of the changes that git was able to merge automatically are
+already added to the index file, so <a href="git-diff.html" target="_top">git-diff(1)</a> shows only
+the conflicts. Also, it uses a somewhat unusual syntax:</p><div class="literallayout"><p>$ git diff<br>
+diff --cc file.txt<br>
+index 802992c,2b60207..0000000<br>
+--- a/file.txt<br>
++++ b/file.txt<br>
+@@@ -1,1 -1,1 +1,5 @@@<br>
+++<<<<<<< HEAD:file.txt<br>
+ +Hello world<br>
+++=======<br>
++ Goodbye<br>
+++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</p></div><p>Recall that the commit which will be commited after we resolve this
+conflict will have two parents instead of the usual one: one parent
+will be HEAD, the tip of the current branch; the other will be the
+tip of the other branch, which is stored temporarily in MERGE_HEAD.</p><p>The diff above shows the differences between the working-tree version
+of file.txt and two previous version: one version from HEAD, and one
+from MERGE_HEAD. So instead of preceding each line by a single "+"
+or "-", it now uses two columns: the first column is used for
+differences between the first parent and the working directory copy,
+and the second for differences between the second parent and the
+working directory copy. Thus after resolving the conflict in the
+obvious way, the diff will look like:</p><div class="literallayout"><p>$ git diff<br>
+diff --cc file.txt<br>
+index 802992c,2b60207..0000000<br>
+--- a/file.txt<br>
++++ b/file.txt<br>
+@@@ -1,1 -1,1 +1,1 @@@<br>
+- Hello world<br>
+ -Goodbye<br>
+++Goodbye world</p></div><p>This shows that our resolved version deleted "Hello world" from the
+first parent, deleted "Goodbye" from the second parent, and added
+"Goodbye world", which was previously absent from both.</p><p>The <a href="git-log.html" target="_top">git-log(1)</a> command also provides special help for merges:</p><div class="literallayout"><p>$ git log --merge</p></div><p>This will list all commits which exist only on HEAD or on MERGE_HEAD,
+and which touch an unmerged file.</p><p>We can now add the resolved version to the index and commit:</p><div class="literallayout"><p>$ git add file.txt<br>
+$ git commit</p></div><p>Note that the commit message will already be filled in for you with
+some information about the merge. Normally you can just use this
+default message unchanged, but you may add additional commentary of
+your own if desired.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="undoing-a-merge"></a>undoing a merge</h2></div></div></div><p>If you get stuck and decide to just give up and throw the whole mess
+away, you can always return to the pre-merge state with</p><div class="literallayout"><p>$ git reset --hard HEAD</p></div><p>Or, if you've already commited the merge that you want to throw away,</p><div class="literallayout"><p>$ git reset --hard HEAD^</p></div><p>However, this last command can be dangerous in some cases—never
+throw away a commit you have already committed if that commit may
+itself have been merged into another branch, as doing so may confuse
+further merges.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275420"></a>Fast-forward merges</h2></div></div></div><p>There is one special case not mentioned above, which is treated
+differently. Normally, a merge results in a merge commit, with two
+parents, one pointing at each of the two lines of development that
+were merged.</p><p>However, if one of the two lines of development is completely
+contained within the other—so every commit present in the one is
+already contained in the other—then git just performs a
+<a href="#fast-forwards" title="Understanding git history: fast-forwards">fast forward</a>; the head of the current branch is
+moved forward to point at the head of the merged-in branch, without
+any new commits being created.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275449"></a>Fixing mistakes</h2></div></div></div><p>If you've messed up the working tree, but haven't yet committed your
+mistake, you can return the entire working tree to the last committed
+state with</p><div class="literallayout"><p>$ git reset --hard HEAD</p></div><p>If you make a commit that you later wish you hadn't, there are two
+fundamentally different ways to fix the problem:</p><div class="orderedlist"><ol type="1"><li>
+You can create a new commit that undoes whatever was done
+ by the previous commit. This is the correct thing if your
+ mistake has already been made public.
+</li><li>
+You can go back and modify the old commit. You should
+ never do this if you have already made the history public;
+ git does not normally expect the "history" of a project to
+ change, and cannot correctly perform repeated merges from
+ a branch that has had its history changed.
+</li></ol></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id275502"></a>Fixing a mistake with a new commit</h3></div></div></div><p>Creating a new commit that reverts an earlier change is very easy;
+just pass the <a href="git-revert.html" target="_top">git-revert(1)</a> command a reference to the bad
+commit; for example, to revert the most recent commit:</p><div class="literallayout"><p>$ git revert HEAD</p></div><p>This will create a new commit which undoes the change in HEAD. You
+will be given a chance to edit the commit message for the new commit.</p><p>You can also revert an earlier change, for example, the next-to-last:</p><div class="literallayout"><p>$ git revert HEAD^</p></div><p>In this case git will attempt to undo the old change while leaving
+intact any changes made since then. If more recent changes overlap
+with the changes to be reverted, then you will be asked to fix
+conflicts manually, just as in the case of <a href="#resolving-a-merge" title="Resolving a merge">resolving a merge</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id275560"></a>Fixing a mistake by editing history</h3></div></div></div><p>If the problematic commit is the most recent commit, and you have not
+yet made that commit public, then you may just
+<a href="#undoing-a-merge" title="undoing a merge">destroy it using git-reset</a>.</p><p>Alternatively, you
+can edit the working directory and update the index to fix your
+mistake, just as if you were going to <a href="#how-to-make-a-commit" title="how to make a commit">create a new commit</a>, then run</p><div class="literallayout"><p>$ git commit --amend</p></div><p>which will replace the old commit by a new commit incorporating your
+changes, giving you a chance to edit the old commit message first.</p><p>Again, you should never do this to a commit that may already have
+been merged into another branch; use <a href="git-revert.html" target="_top">git-revert(1)</a> instead in
+that case.</p><p>It is also possible to edit commits further back in the history, but
+this is an advanced topic to be left for
+<a href="#cleaning-up-history" title="Chapter 6. Rewriting history and maintaining patch series">another chapter</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id275631"></a>Checking out an old version of a file</h3></div></div></div><p>In the process of undoing a previous bad change, you may find it
+useful to check out an older version of a particular file using
+<a href="git-checkout.html" target="_top">git-checkout(1)</a>. We've used git checkout before to switch
+branches, but it has quite different behavior if it is given a path
+name: the command</p><div class="literallayout"><p>$ git checkout HEAD^ path/to/file</p></div><p>replaces path/to/file by the contents it had in the commit HEAD^, and
+also updates the index to match. It does not change branches.</p><p>If you just want to look at an old version of the file, without
+modifying the working directory, you can do that with
+<a href="git-show.html" target="_top">git-show(1)</a>:</p><div class="literallayout"><p>$ git show HEAD^ path/to/file</p></div><p>which will display the given version of the file.</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275689"></a>Ensuring good performance</h2></div></div></div><p>On large repositories, git depends on compression to keep the history
+information from taking up to much space on disk or in memory.</p><p>This compression is not performed automatically. Therefore you
+should occasionally run <a href="git-gc.html" target="_top">git-gc(1)</a>:</p><div class="literallayout"><p>$ git gc</p></div><p>to recompress the archive. This can be very time-consuming, so
+you may prefer to run git-gc when you are not doing other work.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id275727"></a>Ensuring reliability</h2></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id275732"></a>Checking the repository for corruption</h3></div></div></div><p>The <a href="git-fsck.html" target="_top">git-fsck(1)</a> command runs a number of self-consistency checks
+on the repository, and reports on any problems. This may take some
+time. The most common warning by far is about "dangling" objects:</p><div class="literallayout"><p>$ git fsck<br>
+dangling commit 7281251ddd2a61e38657c827739c57015671a6b3<br>
+dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63<br>
+dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5<br>
+dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb<br>
+dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f<br>
+dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e<br>
+dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085<br>
+dangling tree b24c2473f1fd3d91352a624795be026d64c8841f<br>
+...</p></div><p>Dangling objects are objects that are harmless, but also unnecessary;
+you can remove them at any time with <a href="git-prune.html" target="_top">git-prune(1)</a> or the —prune
+option to <a href="git-gc.html" target="_top">git-gc(1)</a>:</p><div class="literallayout"><p>$ git gc --prune</p></div><p>This may be time-consuming. Unlike most other git operations (including
+git-gc when run without any options), it is not safe to prune while
+other git operations are in progress in the same repository.</p><p>For more about dangling objects, see <a href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id275807"></a>Recovering lost changes</h3></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id275813"></a>Reflogs</h4></div></div></div><p>Say you modify a branch with <a href="git-reset.html" target="_top">git-reset(1)</a> —hard, and then
+realize that the branch was the only reference you had to that point in
+history.</p><p>Fortunately, git also keeps a log, called a "reflog", of all the
+previous values of each branch. So in this case you can still find the
+old history using, for example,</p><div class="literallayout"><p>$ git log master@{1}</p></div><p>This lists the commits reachable from the previous version of the head.
+This syntax can be used to with any git command that accepts a commit,
+not just with git log. Some other examples:</p><div class="literallayout"><p>$ git show master@{2} # See where the branch pointed 2,<br>
+$ git show master@{3} # 3, ... changes ago.<br>
+$ gitk master@{yesterday} # See where it pointed yesterday,<br>
+$ gitk master@{"1 week ago"} # ... or last week</p></div><p>The reflogs are kept by default for 30 days, after which they may be
+pruned. See <a href="git-reflog.html" target="_top">git-reflog(1)</a> and <a href="git-gc.html" target="_top">git-gc(1)</a> to learn
+how to control this pruning, and see the "SPECIFYING REVISIONS"
+section of <a href="git-rev-parse.html" target="_top">git-rev-parse(1)</a> for details.</p><p>Note that the reflog history is very different from normal git history.
+While normal history is shared by every repository that works on the
+same project, the reflog history is not shared: it tells you only about
+how the branches in your local repository have changed over time.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id275891"></a>Examining dangling objects</h4></div></div></div><p>In some situations the reflog may not be able to save you. For
+example, suppose you delete a branch, then realize you need the history
+it pointed you. The reflog is also deleted; however, if you have not
+yet pruned the repository, then you may still be able to find
+the lost commits; run git-fsck and watch for output that mentions
+"dangling commits":</p><div class="literallayout"><p>$ git fsck<br>
+dangling commit 7281251ddd2a61e38657c827739c57015671a6b3<br>
+dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63<br>
+dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5<br>
+...</p></div><p>and watch for output that mentions "dangling commits". You can examine
+one of those dangling commits with, for example,</p><div class="literallayout"><p>$ gitk 7281251ddd --not --all</p></div><p>which does what it sounds like: it says that you want to see the commit
+history that is described by the dangling commit(s), but not the
+history that is described by all your existing branches and tags. Thus
+you get exactly the history reachable from that commit that is lost.
+(And notice that it might not be just one commit: we only report the
+"tip of the line" as being dangling, but there might be a whole deep
+and complex commit history that was gotten dropped.)</p><p>If you decide you want the history back, you can always create a new
+reference pointing to it, for example, a new branch:</p><div class="literallayout"><p>$ git branch recovered-branch 7281251ddd</p></div></div></div></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id275958"></a>Chapter 5. Sharing development with others</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#getting-updates-with-git-pull">Getting updates with git pull</a></span></dt><dt><span class="section"><a href="#id276090">Submitting patches to a project</a></span></dt><dt><span class="section"><a href="#id276139">Importing patches to a project</a></span></dt><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via http</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a git repository via the git protocol</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#id276551">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#id276570">Allow web browsing of a repository</a></span></dt><dt><span class="section"><a href="#id276583">Examples</a></span></dt></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="getting-updates-with-git-pull"></a>Getting updates with git pull</h2></div></div></div><p>After you clone a repository and make a few changes of your own, you
+may wish to check the original repository for updates and merge them
+into your own work.</p><p>We have already seen <a href="#Updating-a-repository-with-git-fetch" title="Updating a repository with git fetch">how to keep remote tracking branches up to date</a> with <a href="git-fetch.html" target="_top">git-fetch(1)</a>,
+and how to merge two branches. So you can merge in changes from the
+original repository's master branch with:</p><div class="literallayout"><p>$ git fetch<br>
+$ git merge origin/master</p></div><p>However, the <a href="git-pull.html" target="_top">git-pull(1)</a> command provides a way to do this in
+one step:</p><div class="literallayout"><p>$ git pull origin master</p></div><p>In fact, "origin" is normally the default repository to pull from,
+and the default branch is normally the HEAD of the remote repository,
+so often you can accomplish the above with just</p><div class="literallayout"><p>$ git pull</p></div><p>See the descriptions of the branch.<name>.remote and
+branch.<name>.merge options in <a href="git-config.html" target="_top">git-config(1)</a> to learn
+how to control these defaults depending on the current branch.</p><p>In addition to saving you keystrokes, "git pull" also helps you by
+producing a default commit message documenting the branch and
+repository that you pulled from.</p><p>(But note that no such commit will be created in the case of a
+<a href="#fast-forwards" title="Understanding git history: fast-forwards">fast forward</a>; instead, your branch will just be
+updated to point to the latest commit from the upstream branch).</p><p>The git-pull command can also be given "." as the "remote" repository,
+in which case it just merges in a branch from the current repository; so
+the commands</p><div class="literallayout"><p>$ git pull . branch<br>
+$ git merge branch</p></div><p>are roughly equivalent. The former is actually very commonly used.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276090"></a>Submitting patches to a project</h2></div></div></div><p>If you just have a few changes, the simplest way to submit them may
+just be to send them as patches in email:</p><p>First, use <a href="git-format-patch.html" target="_top">git-format-patch(1)</a>; for example:</p><div class="literallayout"><p>$ git format-patch origin</p></div><p>will produce a numbered series of files in the current directory, one
+for each patch in the current branch but not in origin/HEAD.</p><p>You can then import these into your mail client and send them by
+hand. However, if you have a lot to send at once, you may prefer to
+use the <a href="git-send-email.html" target="_top">git-send-email(1)</a> script to automate the process.
+Consult the mailing list for your project first to determine how they
+prefer such patches be handled.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276139"></a>Importing patches to a project</h2></div></div></div><p>Git also provides a tool called <a href="git-am.html" target="_top">git-am(1)</a> (am stands for
+"apply mailbox"), for importing such an emailed series of patches.
+Just save all of the patch-containing messages, in order, into a
+single mailbox file, say "patches.mbox", then run</p><div class="literallayout"><p>$ git am -3 patches.mbox</p></div><p>Git will apply each patch in order; if any conflicts are found, it
+will stop, and you can fix the conflicts as described in
+"<a href="#resolving-a-merge" title="Resolving a merge">Resolving a merge</a>". (The "-3" option tells
+git to perform a merge; if you would prefer it just to abort and
+leave your tree and index untouched, you may omit that option.)</p><p>Once the index is updated with the results of the conflict
+resolution, instead of creating a new commit, just run</p><div class="literallayout"><p>$ git am --resolved</p></div><p>and git will create the commit for you and continue applying the
+remaining patches from the mailbox.</p><p>The final result will be a series of commits, one for each patch in
+the original mailbox, with authorship and commit log message each
+taken from the message containing each patch.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="setting-up-a-public-repository"></a>Setting up a public repository</h2></div></div></div><p>Another way to submit changes to a project is to simply tell the
+maintainer of that project to pull from your repository, exactly as
+you did in the section "<a href="#getting-updates-with-git-pull" title="Getting updates with git pull">Getting updates with git pull</a>".</p><p>If you and maintainer both have accounts on the same machine, then
+then you can just pull changes from each other's repositories
+directly; note that all of the command (<a href="git-clone.html" target="_top">git-clone(1)</a>,
+git-fetch[1], git-pull[1], etc.) which accept a URL as an argument
+will also accept a local file patch; so, for example, you can
+use</p><div class="literallayout"><p>$ git clone /path/to/repository<br>
+$ git pull /path/to/other/repository</p></div><p>If this sort of setup is inconvenient or impossible, another (more
+common) option is to set up a public repository on a public server.
+This also allows you to cleanly separate private work in progress
+from publicly visible work.</p><p>You will continue to do your day-to-day work in your personal
+repository, but periodically "push" changes from your personal
+repository into your public repository, allowing other developers to
+pull from that repository. So the flow of changes, in a situation
+where there is one other developer with a public repository, looks
+like this:</p><pre class="literallayout"> you push
+your personal repo ------------------> your public repo
+ ^ |
+ | |
+ | you pull | they pull
+ | |
+ | |
+ | they push V
+their public repo <------------------- their repo</pre><p>Now, assume your personal repository is in the directory ~/proj. We
+first create a new clone of the repository:</p><div class="literallayout"><p>$ git clone --bare proj-clone.git</p></div><p>The resulting directory proj-clone.git will contains a "bare" git
+repository—it is just the contents of the ".git" directory, without
+a checked-out copy of a working directory.</p><p>Next, copy proj-clone.git to the server where you plan to host the
+public repository. You can use scp, rsync, or whatever is most
+convenient.</p><p>If somebody else maintains the public server, they may already have
+set up a git service for you, and you may skip to the section
+"<a href="#pushing-changes-to-a-public-repository" title="Pushing changes to a public repository">Pushing changes to a public repository</a>", below.</p><p>Otherwise, the following sections explain how to export your newly
+created public repository:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exporting-via-http"></a>Exporting a git repository via http</h2></div></div></div><p>The git protocol gives better performance and reliability, but on a
+host with a web server set up, http exports may be simpler to set up.</p><p>All you need to do is place the newly created bare git repository in
+a directory that is exported by the web server, and make some
+adjustments to give web clients some extra information they need:</p><div class="literallayout"><p>$ mv proj.git /home/you/public_html/proj.git<br>
+$ cd proj.git<br>
+$ git update-server-info<br>
+$ chmod a+x hooks/post-update</p></div><p>(For an explanation of the last two lines, see
+<a href="git-update-server-info.html" target="_top">git-update-server-info(1)</a>, and the documentation
+<a href="hooks.txt" target="_top">Hooks used by git</a>.)</p><p>Advertise the url of proj.git. Anybody else should then be able to
+clone or pull from that url, for example with a commandline like:</p><div class="literallayout"><p>$ git clone http://yourserver.com/~you/proj.git</p></div><p>(See also
+<a href="howto/setup-git-server-over-http.txt" target="_top">setup-git-server-over-http</a>
+for a slightly more sophisticated setup using WebDAV which also
+allows pushing over http.)</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exporting-via-git"></a>Exporting a git repository via the git protocol</h2></div></div></div><p>This is the preferred method.</p><p>For now, we refer you to the <a href="git-daemon.html" target="_top">git-daemon(1)</a> man page for
+instructions. (See especially the examples section.)</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="pushing-changes-to-a-public-repository"></a>Pushing changes to a public repository</h2></div></div></div><p>Note that the two techniques outline above (exporting via
+<a href="#exporting-via-http" title="Exporting a git repository via http">http</a> or <a href="#exporting-via-git" title="Exporting a git repository via the git protocol">git</a>) allow other
+maintainers to fetch your latest changes, but they do not allow write
+access, which you will need to update the public repository with the
+latest changes created in your private repository.</p><p>The simplest way to do this is using <a href="git-push.html" target="_top">git-push(1)</a> and ssh; to
+update the remote branch named "master" with the latest state of your
+branch named "master", run</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git master:master</p></div><p>or just</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git master</p></div><p>As with git-fetch, git-push will complain if this does not result in
+a <a href="#fast-forwards" title="Understanding git history: fast-forwards">fast forward</a>. Normally this is a sign of
+something wrong. However, if you are sure you know what you're
+doing, you may force git-push to perform the update anyway by
+proceeding the branch name by a plus sign:</p><div class="literallayout"><p>$ git push ssh://yourserver.com/~you/proj.git +master</p></div><p>As with git-fetch, you may also set up configuration options to
+save typing; so, for example, after</p><div class="literallayout"><p>$ cat >.git/config <<EOF<br>
+[remote "public-repo"]<br>
+ url = ssh://yourserver.com/~you/proj.git<br>
+EOF</p></div><p>you should be able to perform the above push with just</p><div class="literallayout"><p>$ git push public-repo master</p></div><p>See the explanations of the remote.<name>.url, branch.<name>.remote,
+and remote.<name>.push options in <a href="git-config.html" target="_top">git-config(1)</a> for
+details.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276551"></a>Setting up a shared repository</h2></div></div></div><p>Another way to collaborate is by using a model similar to that
+commonly used in CVS, where several developers with special rights
+all push to and pull from a single shared repository. See
+<a href="cvs-migration.txt" target="_top">git for CVS users</a> for instructions on how to
+set this up.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276570"></a>Allow web browsing of a repository</h2></div></div></div><p>The gitweb cgi script provides users an easy way to browse your
+project's files and history without having to install git; see the file
+gitweb/README in the git source tree for instructions on setting it up.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276583"></a>Examples</h2></div></div></div><p>TODO: topic branches, typical roles as in everyday.txt, ?</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="cleaning-up-history"></a>Chapter 6. Rewriting history and maintaining patch series</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id276614">Creating the perfect patch series</a></span></dt><dt><span class="section"><a href="#id276689">Keeping a patch series up to date using git-rebase</a></span></dt><dt><span class="section"><a href="#id276826">Reordering or selecting from a patch series</a></span></dt><dt><span class="section"><a href="#id276886">Other tools</a></span></dt><dt><span class="section"><a href="#id276898">Problems with rewriting history</a></span></dt></dl></div><p>Normally commits are only added to a project, never taken away or
+replaced. Git is designed with this assumption, and violating it will
+cause git's merge machinery (for example) to do the wrong thing.</p><p>However, there is a situation in which it can be useful to violate this
+assumption.</p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276614"></a>Creating the perfect patch series</h2></div></div></div><p>Suppose you are a contributor to a large project, and you want to add a
+complicated feature, and to present it to the other developers in a way
+that makes it easy for them to read your changes, verify that they are
+correct, and understand why you made each change.</p><p>If you present all of your changes as a single patch (or commit), they
+may find it is too much to digest all at once.</p><p>If you present them with the entire history of your work, complete with
+mistakes, corrections, and dead ends, they may be overwhelmed.</p><p>So the ideal is usually to produce a series of patches such that:</p><div class="orderedlist"><ol type="1"><li>
+Each patch can be applied in order.
+</li><li>
+Each patch includes a single logical change, together with a
+ message explaining the change.
+</li><li>
+No patch introduces a regression: after applying any initial
+ part of the series, the resulting project still compiles and
+ works, and has no bugs that it didn't have before.
+</li><li>
+The complete series produces the same end result as your own
+ (probably much messier!) development process did.
+</li></ol></div><p>We will introduce some tools that can help you do this, explain how to
+use them, and then explain some of the problems that can arise because
+you are rewriting history.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276689"></a>Keeping a patch series up to date using git-rebase</h2></div></div></div><p>Suppose you have a series of commits in a branch "mywork", which
+originally branched off from "origin".</p><p>Suppose you create a branch "mywork" on a remote-tracking branch
+"origin", and created some commits on top of it:</p><div class="literallayout"><p>$ git checkout -b mywork origin<br>
+$ vi file.txt<br>
+$ git commit<br>
+$ vi otherfile.txt<br>
+$ git commit<br>
+...</p></div><p>You have performed no merges into mywork, so it is just a simple linear
+sequence of patches on top of "origin":</p><pre class="literallayout">o--o--o <-- origin
+ o--o--o <-- mywork</pre><p>Some more interesting work has been done in the upstream project, and
+"origin" has advanced:</p><pre class="literallayout">o--o--O--o--o--o <-- origin
+ a--b--c <-- mywork</pre><p>At this point, you could use "pull" to merge your changes back in;
+the result would create a new merge commit, like this:</p><pre class="literallayout">o--o--O--o--o--o <-- origin
+ \ a--b--c--m <-- mywork</pre><p>However, if you prefer to keep the history in mywork a simple series of
+commits without any merges, you may instead choose to use
+<a href="git-rebase.html" target="_top">git-rebase(1)</a>:</p><div class="literallayout"><p>$ git checkout mywork<br>
+$ git rebase origin</p></div><p>This will remove each of your commits from mywork, temporarily saving
+them as patches (in a directory named ".dotest"), update mywork to
+point at the latest version of origin, then apply each of the saved
+patches to the new mywork. The result will look like:</p><pre class="literallayout">o--o--O--o--o--o <-- origin
+ a'--b'--c' <-- mywork</pre><p>In the process, it may discover conflicts. In that case it will stop
+and allow you to fix the conflicts; after fixing conflicts, use "git
+add" to update the index with those contents, and then, instead of
+running git-commit, just run</p><div class="literallayout"><p>$ git rebase --continue</p></div><p>and git will continue applying the rest of the patches.</p><p>At any point you may use the —abort option to abort this process and
+return mywork to the state it had before you started the rebase:</p><div class="literallayout"><p>$ git rebase --abort</p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276826"></a>Reordering or selecting from a patch series</h2></div></div></div><p>Given one existing commit, the <a href="git-cherry-pick.html" target="_top">git-cherry-pick(1)</a> command
+allows you to apply the change introduced by that commit and create a
+new commit that records it. So, for example, if "mywork" points to a
+series of patches on top of "origin", you might do something like:</p><div class="literallayout"><p>$ git checkout -b mywork-new origin<br>
+$ gitk origin..mywork &</p></div><p>And browse through the list of patches in the mywork branch using gitk,
+applying them (possibly in a different order) to mywork-new using
+cherry-pick, and possibly modifying them as you go using commit
+—amend.</p><p>Another technique is to use git-format-patch to create a series of
+patches, then reset the state to before the patches:</p><div class="literallayout"><p>$ git format-patch origin<br>
+$ git reset --hard origin</p></div><p>Then modify, reorder, or eliminate patches as preferred before applying
+them again with <a href="git-am.html" target="_top">git-am(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276886"></a>Other tools</h2></div></div></div><p>There are numerous other tools, such as stgit, which exist for the
+purpose of maintaining a patch series. These are out of the scope of
+this manual.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276898"></a>Problems with rewriting history</h2></div></div></div><p>The primary problem with rewriting the history of a branch has to do
+with merging. Suppose somebody fetches your branch and merges it into
+their branch, with a result something like this:</p><pre class="literallayout">o--o--O--o--o--o <-- origin
+ \ t--t--t--m <-- their branch:</pre><p>Then suppose you modify the last three commits:</p><pre class="literallayout"> o--o--o <-- new head of origin
+ /
+o--o--O--o--o--o <-- old head of origin</pre><p>If we examined all this history together in one repository, it will
+look like:</p><pre class="literallayout"> o--o--o <-- new head of origin
+ /
+o--o--O--o--o--o <-- old head of origin
+ \ t--t--t--m <-- their branch:</pre><p>Git has no way of knowing that the new head is an updated version of
+the old head; it treats this situation exactly the same as it would if
+two developers had independently done the work on the old and new heads
+in parallel. At this point, if someone attempts to merge the new head
+in to their branch, git will attempt to merge together the two (old and
+new) lines of development, instead of trying to replace the old by the
+new. The results are likely to be unexpected.</p><p>You may still choose to publish branches whose history is rewritten,
+and it may be useful for others to be able to fetch those branches in
+order to examine or test them, but they should not attempt to pull such
+branches into their own work.</p><p>For true distributed development that supports proper merging,
+published branches should never be rewritten.</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id276970"></a>Chapter 7. Advanced branch management</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id276976">Fetching individual branches</a></span></dt><dt><span class="section"><a href="#fast-forwards">Understanding git history: fast-forwards</a></span></dt><dt><span class="section"><a href="#id277096">Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="section"><a href="#id277123">Configuring remote branches</a></span></dt></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id276976"></a>Fetching individual branches</h2></div></div></div><p>Instead of using <a href="git-remote.html" target="_top">git-remote(1)</a>, you can also choose just
+to update one branch at a time, and to store it locally under an
+arbitrary name:</p><div class="literallayout"><p>$ git fetch origin todo:my-todo-work</p></div><p>The first argument, "origin", just tells git to fetch from the
+repository you originally cloned from. The second argument tells git
+to fetch the branch named "todo" from the remote repository, and to
+store it locally under the name refs/heads/my-todo-work.</p><p>You can also fetch branches from other repositories; so</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:example-master</p></div><p>will create a new branch named "example-master" and store in it the
+branch named "master" from the repository at the given URL. If you
+already have a branch named example-master, it will attempt to
+"fast-forward" to the commit given by example.com's master branch. So
+next we explain what a fast-forward is:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fast-forwards"></a>Understanding git history: fast-forwards</h2></div></div></div><p>In the previous example, when updating an existing branch, "git
+fetch" checks to make sure that the most recent commit on the remote
+branch is a descendant of the most recent commit on your copy of the
+branch before updating your copy of the branch to point at the new
+commit. Git calls this process a "fast forward".</p><p>A fast forward looks something like this:</p><pre class="literallayout">o--o--o--o <-- old head of the branch
+ o--o--o <-- new head of the branch</pre><p>In some cases it is possible that the new head will <span class="strong"><strong>not</strong></span> actually be
+a descendant of the old head. For example, the developer may have
+realized she made a serious mistake, and decided to backtrack,
+resulting in a situation like:</p><pre class="literallayout">o--o--o--o--a--b <-- old head of the branch
+ o--o--o <-- new head of the branch</pre><p>In this case, "git fetch" will fail, and print out a warning.</p><p>In that case, you can still force git to update to the new head, as
+described in the following section. However, note that in the
+situation above this may mean losing the commits labeled "a" and "b",
+unless you've already created a reference of your own pointing to
+them.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277096"></a>Forcing git fetch to do non-fast-forward updates</h2></div></div></div><p>If git fetch fails because the new head of a branch is not a
+descendant of the old head, you may force the update with:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git +master:refs/remotes/example/master</p></div><p>Note the addition of the "+" sign. Be aware that commits which the
+old version of example/master pointed at may be lost, as we saw in
+the previous section.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277123"></a>Configuring remote branches</h2></div></div></div><p>We saw above that "origin" is just a shortcut to refer to the
+repository which you originally cloned from. This information is
+stored in git configuration variables, which you can see using
+<a href="git-config.html" target="_top">git-config(1)</a>:</p><div class="literallayout"><p>$ git config -l<br>
+core.repositoryformatversion=0<br>
+core.filemode=true<br>
+core.logallrefupdates=true<br>
+remote.origin.url=git://git.kernel.org/pub/scm/git/git.git<br>
+remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*<br>
+branch.master.remote=origin<br>
+branch.master.merge=refs/heads/master</p></div><p>If there are other repositories that you also use frequently, you can
+create similar configuration options to save typing; for example,
+after</p><div class="literallayout"><p>$ git config remote.example.url git://example.com/proj.git</p></div><p>then the following two commands will do the same thing:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:refs/remotes/example/master<br>
+$ git fetch example master:refs/remotes/example/master</p></div><p>Even better, if you add one more option:</p><div class="literallayout"><p>$ git config remote.example.fetch master:refs/remotes/example/master</p></div><p>then the following commands will all do the same thing:</p><div class="literallayout"><p>$ git fetch git://example.com/proj.git master:ref/remotes/example/master<br>
+$ git fetch example master:ref/remotes/example/master<br>
+$ git fetch example example/master<br>
+$ git fetch example</p></div><p>You can also add a "+" to force the update each time:</p><div class="literallayout"><p>$ git config remote.example.fetch +master:ref/remotes/example/master</p></div><p>Don't do this unless you're sure you won't mind "git fetch" possibly
+throwing away commits on mybranch.</p><p>Also note that all of the above configuration can be performed by
+directly editing the file .git/config instead of using
+<a href="git-config.html" target="_top">git-config(1)</a>.</p><p>See <a href="git-config.html" target="_top">git-config(1)</a> for more details on the configuration
+options mentioned above.</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id277247"></a>Chapter 8. Git internals</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id277258">The Object Database</a></span></dt><dt><span class="section"><a href="#id277374">Blob Object</a></span></dt><dt><span class="section"><a href="#id277417">Tree Object</a></span></dt><dt><span class="section"><a href="#id277495">Commit Object</a></span></dt><dt><span class="section"><a href="#id277541">Trust</a></span></dt><dt><span class="section"><a href="#id277592">Tag Object</a></span></dt><dt><span class="section"><a href="#id277638">The "index" aka "Current Directory Cache"</a></span></dt><dt><span class="section"><a href="#id277713">The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#id277732">working directory -> index</a></span></dt><dt><span class="section"><a href="#id277821">index -> object database</a></span></dt><dt><span class="section"><a href="#id277850">object database -> index</a></span></dt><dt><span class="section"><a href="#id277880">index -> working directory</a></span></dt><dt><span class="section"><a href="#id277944">Tying it all together</a></span></dt></dl></dd><dt><span class="section"><a href="#id278039">Examining the data</a></span></dt><dt><span class="section"><a href="#id278117">Merging multiple trees</a></span></dt><dt><span class="section"><a href="#id278204">Merging multiple trees, continued</a></span></dt><dt><span class="section"><a href="#id278464">How git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt></dl></div><p>There are two object abstractions: the "object database", and the
+"current directory cache" aka "index".</p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277258"></a>The Object Database</h2></div></div></div><p>The object database is literally just a content-addressable collection
+of objects. All objects are named by their content, which is
+approximated by the SHA1 hash of the object itself. Objects may refer
+to other objects (by referencing their SHA1 hash), and so you can
+build up a hierarchy of objects.</p><p>All objects have a statically determined "type" aka "tag", which is
+determined at object creation time, and which identifies the format of
+the object (i.e. how it is used, and how it can refer to other
+objects). There are currently four different object types: "blob",
+"tree", "commit" and "tag".</p><p>A "blob" object cannot refer to any other object, and is, like the type
+implies, a pure storage object containing some user data. It is used to
+actually store the file data, i.e. a blob object is associated with some
+particular version of some file.</p><p>A "tree" object is an object that ties one or more "blob" objects into a
+directory structure. In addition, a tree object can refer to other tree
+objects, thus creating a directory hierarchy.</p><p>A "commit" object ties such directory hierarchies together into
+a DAG of revisions - each "commit" is associated with exactly one tree
+(the directory hierarchy at the time of the commit). In addition, a
+"commit" refers to one or more "parent" commit objects that describe the
+history of how we arrived at that directory hierarchy.</p><p>As a special case, a commit object with no parents is called the "root"
+object, and is the point of an initial project commit. Each project
+must have at least one root, and while you can tie several different
+root objects together into one project by creating a commit object which
+has two or more separate roots as its ultimate parents, that's probably
+just going to confuse people. So aim for the notion of "one root object
+per project", even if git itself does not enforce that.</p><p>A "tag" object symbolically identifies and can be used to sign other
+objects. It contains the identifier and type of another object, a
+symbolic name (of course!) and, optionally, a signature.</p><p>Regardless of object type, all objects share the following
+characteristics: they are all deflated with zlib, and have a header
+that not only specifies their type, but also provides size information
+about the data in the object. It's worth noting that the SHA1 hash
+that is used to name the object is the hash of the original data
+plus this header, so <code class="literal">sha1sum</code> <span class="emphasis"><em>file</em></span> does not match the object name
+for <span class="emphasis"><em>file</em></span>.
+(Historical note: in the dawn of the age of git the hash
+was the sha1 of the <span class="emphasis"><em>compressed</em></span> object.)</p><p>As a result, the general consistency of an object can always be tested
+independently of the contents or the type of the object: all objects can
+be validated by verifying that (a) their hashes match the content of the
+file and (b) the object successfully inflates to a stream of bytes that
+forms a sequence of <ascii type without space> + <space> + <ascii decimal
+size> + <byte\0> + <binary object data>.</p><p>The structured objects can further have their structure and
+connectivity to other objects verified. This is generally done with
+the <code class="literal">git-fsck</code> program, which generates a full dependency graph
+of all objects, and verifies their internal consistency (in addition
+to just verifying their superficial consistency through the hash).</p><p>The object types in some more detail:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277374"></a>Blob Object</h2></div></div></div><p>A "blob" object is nothing but a binary blob of data, and doesn't
+refer to anything else. There is no signature or any other
+verification of the data, so while the object is consistent (it <span class="emphasis"><em>is</em></span>
+indexed by its sha1 hash, so the data itself is certainly correct), it
+has absolutely no other attributes. No name associations, no
+permissions. It is purely a blob of data (i.e. normally "file
+contents").</p><p>In particular, since the blob is entirely defined by its data, if two
+files in a directory tree (or in multiple different versions of the
+repository) have the same contents, they will share the same blob
+object. The object is totally independent of its location in the
+directory tree, and renaming a file does not change the object that
+file is associated with in any way.</p><p>A blob is typically created when <a href="git-update-index.html" target="_top">git-update-index(1)</a>
+is run, and its data can be accessed by <a href="git-cat-file.html" target="_top">git-cat-file(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277417"></a>Tree Object</h2></div></div></div><p>The next hierarchical object type is the "tree" object. A tree object
+is a list of mode/name/blob data, sorted by name. Alternatively, the
+mode data may specify a directory mode, in which case instead of
+naming a blob, that name is associated with another TREE object.</p><p>Like the "blob" object, a tree object is uniquely determined by the
+set contents, and so two separate but identical trees will always
+share the exact same object. This is true at all levels, i.e. it's
+true for a "leaf" tree (which does not refer to any other trees, only
+blobs) as well as for a whole subdirectory.</p><p>For that reason a "tree" object is just a pure data abstraction: it
+has no history, no signatures, no verification of validity, except
+that since the contents are again protected by the hash itself, we can
+trust that the tree is immutable and its contents never change.</p><p>So you can trust the contents of a tree to be valid, the same way you
+can trust the contents of a blob, but you don't know where those
+contents <span class="emphasis"><em>came</em></span> from.</p><p>Side note on trees: since a "tree" object is a sorted list of
+"filename+content", you can create a diff between two trees without
+actually having to unpack two trees. Just ignore all common parts,
+and your diff will look right. In other words, you can effectively
+(and efficiently) tell the difference between any two random trees by
+O(n) where "n" is the size of the difference, rather than the size of
+the tree.</p><p>Side note 2 on trees: since the name of a "blob" depends entirely and
+exclusively on its contents (i.e. there are no names or permissions
+involved), you can see trivial renames or permission changes by
+noticing that the blob stayed the same. However, renames with data
+changes need a smarter "diff" implementation.</p><p>A tree is created with <a href="git-write-tree.html" target="_top">git-write-tree(1)</a> and
+its data can be accessed by <a href="git-ls-tree.html" target="_top">git-ls-tree(1)</a>.
+Two trees can be compared with <a href="git-diff-tree.html" target="_top">git-diff-tree(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277495"></a>Commit Object</h2></div></div></div><p>The "commit" object is an object that introduces the notion of
+history into the picture. In contrast to the other objects, it
+doesn't just describe the physical state of a tree, it describes how
+we got there, and why.</p><p>A "commit" is defined by the tree-object that it results in, the
+parent commits (zero, one or more) that led up to that point, and a
+comment on what happened. Again, a commit is not trusted per se:
+the contents are well-defined and "safe" due to the cryptographically
+strong signatures at all levels, but there is no reason to believe
+that the tree is "good" or that the merge information makes sense.
+The parents do not have to actually have any relationship with the
+result, for example.</p><p>Note on commits: unlike real SCM's, commits do not contain
+rename information or file mode change information. All of that is
+implicit in the trees involved (the result tree, and the result trees
+of the parents), and describing that makes no sense in this idiotic
+file manager.</p><p>A commit is created with <a href="git-commit-tree.html" target="_top">git-commit-tree(1)</a> and
+its data can be accessed by <a href="git-cat-file.html" target="_top">git-cat-file(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277541"></a>Trust</h2></div></div></div><p>An aside on the notion of "trust". Trust is really outside the scope
+of "git", but it's worth noting a few things. First off, since
+everything is hashed with SHA1, you <span class="emphasis"><em>can</em></span> trust that an object is
+intact and has not been messed with by external sources. So the name
+of an object uniquely identifies a known state - just not a state that
+you may want to trust.</p><p>Furthermore, since the SHA1 signature of a commit refers to the
+SHA1 signatures of the tree it is associated with and the signatures
+of the parent, a single named commit specifies uniquely a whole set
+of history, with full contents. You can't later fake any step of the
+way once you have the name of a commit.</p><p>So to introduce some real trust in the system, the only thing you need
+to do is to digitally sign just <span class="emphasis"><em>one</em></span> special note, which includes the
+name of a top-level commit. Your digital signature shows others
+that you trust that commit, and the immutability of the history of
+commits tells others that they can trust the whole history.</p><p>In other words, you can easily validate a whole archive by just
+sending out a single email that tells the people the name (SHA1 hash)
+of the top commit, and digitally sign that email using something
+like GPG/PGP.</p><p>To assist in this, git also provides the tag object…</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277592"></a>Tag Object</h2></div></div></div><p>Git provides the "tag" object to simplify creating, managing and
+exchanging symbolic and signed tokens. The "tag" object at its
+simplest simply symbolically identifies another object by containing
+the sha1, type and symbolic name.</p><p>However it can optionally contain additional signature information
+(which git doesn't care about as long as there's less than 8k of
+it). This can then be verified externally to git.</p><p>Note that despite the tag features, "git" itself only handles content
+integrity; the trust framework (and signature provision and
+verification) has to come from outside.</p><p>A tag is created with <a href="git-mktag.html" target="_top">git-mktag(1)</a>,
+its data can be accessed by <a href="git-cat-file.html" target="_top">git-cat-file(1)</a>,
+and the signature can be verified by
+<a href="git-verify-tag.html" target="_top">git-verify-tag(1)</a>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277638"></a>The "index" aka "Current Directory Cache"</h2></div></div></div><p>The index is a simple binary file, which contains an efficient
+representation of a virtual directory content at some random time. It
+does so by a simple array that associates a set of names, dates,
+permissions and content (aka "blob") objects together. The cache is
+always kept ordered by name, and names are unique (with a few very
+specific rules) at any point in time, but the cache has no long-term
+meaning, and can be partially updated at any time.</p><p>In particular, the index certainly does not need to be consistent with
+the current directory contents (in fact, most operations will depend on
+different ways to make the index <span class="emphasis"><em>not</em></span> be consistent with the directory
+hierarchy), but it has three very important attributes:</p><p><span class="emphasis"><em>(a) it can re-generate the full state it caches (not just the
+directory structure: it contains pointers to the "blob" objects so
+that it can regenerate the data too)</em></span></p><p>As a special case, there is a clear and unambiguous one-way mapping
+from a current directory cache to a "tree object", which can be
+efficiently created from just the current directory cache without
+actually looking at any other data. So a directory cache at any one
+time uniquely specifies one and only one "tree" object (but has
+additional data to make it easy to match up that tree object with what
+has happened in the directory)</p><p><span class="emphasis"><em>(b) it has efficient methods for finding inconsistencies between that
+cached state ("tree object waiting to be instantiated") and the
+current state.</em></span></p><p><span class="emphasis"><em>(c) it can additionally efficiently represent information about merge
+conflicts between different tree objects, allowing each pathname to be
+associated with sufficient information about the trees involved that
+you can create a three-way merge between them.</em></span></p><p>Those are the three ONLY things that the directory cache does. It's a
+cache, and the normal operation is to re-generate it completely from a
+known tree object, or update/compare it with a live tree that is being
+developed. If you blow the directory cache away entirely, you generally
+haven't lost any information as long as you have the name of the tree
+that it described.</p><p>At the same time, the index is at the same time also the
+staging area for creating new trees, and creating a new tree always
+involves a controlled modification of the index file. In particular,
+the index file can have the representation of an intermediate tree that
+has not yet been instantiated. So the index can be thought of as a
+write-back cache, which can contain dirty information that has not yet
+been written back to the backing store.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id277713"></a>The Workflow</h2></div></div></div><p>Generally, all "git" operations work on the index file. Some operations
+work <span class="strong"><strong>purely</strong></span> on the index file (showing the current state of the
+index), but most operations move data to and from the index file. Either
+from the database or from the working directory. Thus there are four
+main combinations:</p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id277732"></a>working directory -> index</h3></div></div></div><p>You update the index with information from the working directory with
+the <a href="git-update-index.html" target="_top">git-update-index(1)</a> command. You
+generally update the index information by just specifying the filename
+you want to update, like so:</p><div class="literallayout"><p>$ git-update-index filename</p></div><p>but to avoid common mistakes with filename globbing etc, the command
+will not normally add totally new entries or remove old entries,
+i.e. it will normally just update existing cache entries.</p><p>To tell git that yes, you really do realize that certain files no
+longer exist, or that new files should be added, you
+should use the <code class="literal">—remove</code> and <code class="literal">—add</code> flags respectively.</p><p>NOTE! A <code class="literal">—remove</code> flag does <span class="emphasis"><em>not</em></span> mean that subsequent filenames will
+necessarily be removed: if the files still exist in your directory
+structure, the index will be updated with their new status, not
+removed. The only thing <code class="literal">—remove</code> means is that update-cache will be
+considering a removed file to be a valid thing, and if the file really
+does not exist any more, it will update the index accordingly.</p><p>As a special case, you can also do <code class="literal">git-update-index —refresh</code>, which
+will refresh the "stat" information of each index to match the current
+stat information. It will <span class="emphasis"><em>not</em></span> update the object status itself, and
+it will only update the fields that are used to quickly test whether
+an object still matches its old backing store object.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id277821"></a>index -> object database</h3></div></div></div><p>You write your current index file to a "tree" object with the program</p><div class="literallayout"><p>$ git-write-tree</p></div><p>that doesn't come with any options - it will just write out the
+current index into the set of tree objects that describe that state,
+and it will return the name of the resulting top-level tree. You can
+use that tree to re-generate the index at any time by going in the
+other direction:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id277850"></a>object database -> index</h3></div></div></div><p>You read a "tree" file from the object database, and use that to
+populate (and overwrite - don't do this if your index contains any
+unsaved state that you might want to restore later!) your current
+index. Normal operation is just</p><div class="literallayout"><p>$ git-read-tree <sha1 of tree></p></div><p>and your index file will now be equivalent to the tree that you saved
+earlier. However, that is only your <span class="emphasis"><em>index</em></span> file: your working
+directory contents have not been modified.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id277880"></a>index -> working directory</h3></div></div></div><p>You update your working directory from the index by "checking out"
+files. This is not a very common operation, since normally you'd just
+keep your files updated, and rather than write to your working
+directory, you'd tell the index files about the changes in your
+working directory (i.e. <code class="literal">git-update-index</code>).</p><p>However, if you decide to jump to a new version, or check out somebody
+else's version, or just restore a previous tree, you'd populate your
+index file with read-tree, and then you need to check out the result
+with</p><div class="literallayout"><p>$ git-checkout-index filename</p></div><p>or, if you want to check out all of the index, use <code class="literal">-a</code>.</p><p>NOTE! git-checkout-index normally refuses to overwrite old files, so
+if you have an old version of the tree already checked out, you will
+need to use the "-f" flag (<span class="emphasis"><em>before</em></span> the "-a" flag or the filename) to
+<span class="emphasis"><em>force</em></span> the checkout.</p><p>Finally, there are a few odds and ends which are not purely moving
+from one representation to the other:</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id277944"></a>Tying it all together</h3></div></div></div><p>To commit a tree you have instantiated with "git-write-tree", you'd
+create a "commit" object that refers to that tree and the history
+behind it - most notably the "parent" commits that preceded it in
+history.</p><p>Normally a "commit" has one parent: the previous state of the tree
+before a certain change was made. However, sometimes it can have two
+or more parent commits, in which case we call it a "merge", due to the
+fact that such a commit brings together ("merges") two or more
+previous states represented by other commits.</p><p>In other words, while a "tree" represents a particular directory state
+of a working directory, a "commit" represents that state in "time",
+and explains how we got there.</p><p>You create a commit object by giving it the tree that describes the
+state at the time of the commit, and a list of parents:</p><div class="literallayout"><p>$ git-commit-tree <tree> -p <parent> [-p <parent2> ..]</p></div><p>and then giving the reason for the commit on stdin (either through
+redirection from a pipe or file, or by just typing it at the tty).</p><p>git-commit-tree will return the name of the object that represents
+that commit, and you should save it away for later use. Normally,
+you'd commit a new <code class="literal">HEAD</code> state, and while git doesn't care where you
+save the note about that state, in practice we tend to just write the
+result to the file pointed at by <code class="literal">.git/HEAD</code>, so that we can always see
+what the last committed state was.</p><p>Here is an ASCII art by Jon Loeliger that illustrates how
+various pieces fit together.</p><div class="literallayout"><p><br>
+ commit-tree<br>
+ commit obj<br>
+ +----+<br>
+ | |<br>
+ | |<br>
+ V V<br>
+ +-----------+<br>
+ | Object DB |<br>
+ | Backing |<br>
+ | Store |<br>
+ +-----------+<br>
+ ^<br>
+ write-tree | |<br>
+ tree obj | |<br>
+ | | read-tree<br>
+ | | tree obj<br>
+ V<br>
+ +-----------+<br>
+ | Index |<br>
+ | "cache" |<br>
+ +-----------+<br>
+ update-index ^<br>
+ blob obj | |<br>
+ | |<br>
+ checkout-index -u | | checkout-index<br>
+ stat | | blob obj<br>
+ V<br>
+ +-----------+<br>
+ | Working |<br>
+ | Directory |<br>
+ +-----------+<br>
+</p></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id278039"></a>Examining the data</h2></div></div></div><p>You can examine the data represented in the object database and the
+index with various helper tools. For every object, you can use
+<a href="git-cat-file.html" target="_top">git-cat-file(1)</a> to examine details about the
+object:</p><div class="literallayout"><p>$ git-cat-file -t <objectname></p></div><p>shows the type of the object, and once you have the type (which is
+usually implicit in where you find the object), you can use</p><div class="literallayout"><p>$ git-cat-file blob|tree|commit|tag <objectname></p></div><p>to show its contents. NOTE! Trees have binary content, and as a result
+there is a special helper for showing that content, called
+<code class="literal">git-ls-tree</code>, which turns the binary content into a more easily
+readable form.</p><p>It's especially instructive to look at "commit" objects, since those
+tend to be small and fairly self-explanatory. In particular, if you
+follow the convention of having the top commit name in <code class="literal">.git/HEAD</code>,
+you can do</p><div class="literallayout"><p>$ git-cat-file commit HEAD</p></div><p>to see what the top commit was.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id278117"></a>Merging multiple trees</h2></div></div></div><p>Git helps you do a three-way merge, which you can expand to n-way by
+repeating the merge procedure arbitrary times until you finally
+"commit" the state. The normal situation is that you'd only do one
+three-way merge (two parents), and commit it, but if you like to, you
+can do multiple parents in one go.</p><p>To do a three-way merge, you need the two sets of "commit" objects
+that you want to merge, use those to find the closest common parent (a
+third "commit" object), and then use those commit objects to find the
+state of the directory ("tree" object) at these points.</p><p>To get the "base" for the merge, you first look up the common parent
+of two commits with</p><div class="literallayout"><p>$ git-merge-base <commit1> <commit2></p></div><p>which will return you the commit they are both based on. You should
+now look up the "tree" objects of those commits, which you can easily
+do with (for example)</p><div class="literallayout"><p>$ git-cat-file commit <commitname> | head -1</p></div><p>since the tree object information is always the first line in a commit
+object.</p><p>Once you know the three trees you are going to merge (the one "original"
+tree, aka the common case, and the two "result" trees, aka the branches
+you want to merge), you do a "merge" read into the index. This will
+complain if it has to throw away your old index contents, so you should
+make sure that you've committed those - in fact you would normally
+always do a merge against your last commit (which should thus match what
+you have in your current index anyway).</p><p>To do the merge, do</p><div class="literallayout"><p>$ git-read-tree -m -u <origtree> <yourtree> <targettree></p></div><p>which will do all trivial merge operations for you directly in the
+index file, and you can just write the result out with
+<code class="literal">git-write-tree</code>.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id278204"></a>Merging multiple trees, continued</h2></div></div></div><p>Sadly, many merges aren't trivial. If there are files that have
+been added.moved or removed, or if both branches have modified the
+same file, you will be left with an index tree that contains "merge
+entries" in it. Such an index tree can <span class="emphasis"><em>NOT</em></span> be written out to a tree
+object, and you will have to resolve any such merge clashes using
+other tools before you can write out the result.</p><p>You can examine such index state with <code class="literal">git-ls-files —unmerged</code>
+command. An example:</p><div class="literallayout"><p>$ git-read-tree -m $orig HEAD $target<br>
+$ git-ls-files --unmerged<br>
+100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c<br>
+100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c<br>
+100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c</p></div><p>Each line of the <code class="literal">git-ls-files —unmerged</code> output begins with
+the blob mode bits, blob SHA1, <span class="emphasis"><em>stage number</em></span>, and the
+filename. The <span class="emphasis"><em>stage number</em></span> is git's way to say which tree it
+came from: stage 1 corresponds to <code class="literal">$orig</code> tree, stage 2 <code class="literal">HEAD</code>
+tree, and stage3 <code class="literal">$target</code> tree.</p><p>Earlier we said that trivial merges are done inside
+<code class="literal">git-read-tree -m</code>. For example, if the file did not change
+from <code class="literal">$orig</code> to <code class="literal">HEAD</code> nor <code class="literal">$target</code>, or if the file changed
+from <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> the same way,
+obviously the final outcome is what is in <code class="literal">HEAD</code>. What the
+above example shows is that file <code class="literal">hello.c</code> was changed from
+<code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> in a different way.
+You could resolve this by running your favorite 3-way merge
+program, e.g. <code class="literal">diff3</code> or <code class="literal">merge</code>, on the blob objects from
+these three stages yourself, like this:</p><div class="literallayout"><p>$ git-cat-file blob 263414f... >hello.c~1<br>
+$ git-cat-file blob 06fa6a2... >hello.c~2<br>
+$ git-cat-file blob cc44c73... >hello.c~3<br>
+$ merge hello.c~2 hello.c~1 hello.c~3</p></div><p>This would leave the merge result in <code class="literal">hello.c~2</code> file, along
+with conflict markers if there are conflicts. After verifying
+the merge result makes sense, you can tell git what the final
+merge result for this file is by:</p><div class="literallayout"><p>$ mv -f hello.c~2 hello.c<br>
+$ git-update-index hello.c</p></div><p>When a path is in unmerged state, running <code class="literal">git-update-index</code> for
+that path tells git to mark the path resolved.</p><p>The above is the description of a git merge at the lowest level,
+to help you understand what conceptually happens under the hood.
+In practice, nobody, not even git itself, uses three <code class="literal">git-cat-file</code>
+for this. There is <code class="literal">git-merge-index</code> program that extracts the
+stages to temporary files and calls a "merge" script on it:</p><div class="literallayout"><p>$ git-merge-index git-merge-one-file hello.c</p></div><p>and that is what higher level <code class="literal">git resolve</code> is implemented with.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id278464"></a>How git stores objects efficiently: pack files</h2></div></div></div><p>We've seen how git stores each object in a file named after the
+object's SHA1 hash.</p><p>Unfortunately this system becomes inefficient once a project has a
+lot of objects. Try this on an old project:</p><div class="literallayout"><p>$ git count-objects<br>
+6930 objects, 47620 kilobytes</p></div><p>The first number is the number of objects which are kept in
+individual files. The second is the amount of space taken up by
+those "loose" objects.</p><p>You can save space and make git faster by moving these loose objects in
+to a "pack file", which stores a group of objects in an efficient
+compressed format; the details of how pack files are formatted can be
+found in <a href="technical/pack-format.txt" target="_top">technical/pack-format.txt</a>.</p><p>To put the loose objects into a pack, just run git repack:</p><div class="literallayout"><p>$ git repack<br>
+Generating pack...<br>
+Done counting 6020 objects.<br>
+Deltifying 6020 objects.<br>
+ 100% (6020/6020) done<br>
+Writing 6020 objects.<br>
+ 100% (6020/6020) done<br>
+Total 6020, written 6020 (delta 4070), reused 0 (delta 0)<br>
+Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.</p></div><p>You can then run</p><div class="literallayout"><p>$ git prune</p></div><p>to remove any of the "loose" objects that are now contained in the
+pack. This will also remove any unreferenced objects (which may be
+created when, for example, you use "git reset" to remove a commit).
+You can verify that the loose objects are gone by looking at the
+.git/objects directory or by running</p><div class="literallayout"><p>$ git count-objects<br>
+0 objects, 0 kilobytes</p></div><p>Although the object files are gone, any commands that refer to those
+objects will work exactly as they did before.</p><p>The <a href="git-gc.html" target="_top">git-gc(1)</a> command performs packing, pruning, and more for
+you, so is normally the only high-level command you need.</p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="dangling-objects"></a>Dangling objects</h2></div></div></div><p>The <a href="git-fsck.html" target="_top">git-fsck(1)</a> command will sometimes complain about dangling
+objects. They are not a problem.</p><p>The most common cause of dangling objects is that you've rebased a
+branch, or you have pulled from somebody else who rebased a branch—see
+<a href="#cleaning-up-history" title="Chapter 6. Rewriting history and maintaining patch series">Chapter 6, <i>Rewriting history and maintaining patch series</i></a>. In that case, the old head of the original
+branch still exists, as does obviously everything it pointed to. The
+branch pointer itself just doesn't, since you replaced it with another
+one.</p><p>There are also other situations too that cause dangling objects. For
+example, a "dangling blob" may arise because you did a "git add" of a
+file, but then, before you actually committed it and made it part of the
+bigger picture, you changed something else in that file and committed
+that <span class="strong"><strong>updated</strong></span> thing - the old state that you added originally ends up
+not being pointed to by any commit or tree, so it's now a dangling blob
+object.</p><p>Similarly, when the "recursive" merge strategy runs, and finds that
+there are criss-cross merges and thus more than one merge base (which is
+fairly unusual, but it does happen), it will generate one temporary
+midway tree (or possibly even more, if you had lots of criss-crossing
+merges and more than two merge bases) as a temporary internal merge
+base, and again, those are real objects, but the end result will not end
+up pointing to them, so they end up "dangling" in your repository.</p><p>Generally, dangling objects aren't anything to worry about. They can
+even be very useful: if you screw something up, the dangling objects can
+be how you recover your old tree (say, you did a rebase, and realized
+that you really didn't want to - you can look at what dangling objects
+you have, and decide to reset your head to some old dangling state).</p><p>For commits, the most useful thing to do with dangling objects tends to
+be to do a simple</p><div class="literallayout"><p>$ gitk <dangling-commit-sha-goes-here> --not --all</p></div><p>For blobs and trees, you can't do the same, but you can examine them.
+You can just do</p><div class="literallayout"><p>$ git show <dangling-blob/tree-sha-goes-here></p></div><p>to show what the contents of the blob were (or, for a tree, basically
+what the "ls" for that directory was), and that may give you some idea
+of what the operation was that left that dangling object.</p><p>Usually, dangling blobs and trees aren't very interesting. They're
+almost always the result of either being a half-way mergebase (the blob
+will often even have the conflict markers from a merge in it, if you
+have had conflicting merges that you fixed up by hand), or simply
+because you interrupted a "git fetch" with ^C or something like that,
+leaving _some_ of the new objects in the object database, but just
+dangling and useless.</p><p>Anyway, once you are sure that you're not interested in any dangling
+state, you can just prune all unreachable objects:</p><div class="literallayout"><p>$ git prune</p></div><p>and they'll be gone. But you should only run "git prune" on a quiescent
+repository - it's kind of like doing a filesystem fsck recovery: you
+don't want to do that while the filesystem is mounted.</p><p>(The same is true of "git-fsck" itself, btw - but since
+git-fsck never actually <span class="strong"><strong>changes</strong></span> the repository, it just reports
+on what it found, git-fsck itself is never "dangerous" to run.
+Running it while somebody is actually changing the repository can cause
+confusing and scary messages, but it won't actually do anything bad. In
+contrast, running "git prune" while somebody is actively changing the
+repository is a <span class="strong"><strong>BAD</strong></span> idea).</p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id278724"></a>Chapter 9. Glossary of git terms</h2></div></div></div><div class="variablelist"><dl><dt><span class="term">
+alternate object database
+</span></dt><dd>
+ Via the alternates mechanism, a repository can inherit part of its
+ object database from another object database, which is called
+ "alternate".
+</dd><dt><span class="term">
+bare repository
+</span></dt><dd>
+ A bare repository is normally an appropriately named
+ directory with a <code class="literal">.git</code> suffix that does not have a
+ locally checked-out copy of any of the files under revision
+ control. That is, all of the <code class="literal">git</code> administrative and
+ control files that would normally be present in the
+ hidden <code class="literal">.git</code> sub-directory are directly present in
+ the <code class="literal">repository.git</code> directory instead, and no other files
+ are present and checked out. Usually publishers of public
+ repositories make bare repositories available.
+</dd><dt><span class="term">
+blob object
+</span></dt><dd>
+ Untyped object, e.g. the contents of a file.
+</dd><dt><span class="term">
+branch
+</span></dt><dd>
+ A non-cyclical graph of revisions, i.e. the complete history of
+ a particular revision, which is called the branch head. The
+ branch heads are stored in <code class="literal">$GIT_DIR/refs/heads/</code>.
+</dd><dt><span class="term">
+cache
+</span></dt><dd>
+ Obsolete for: index.
+</dd><dt><span class="term">
+chain
+</span></dt><dd>
+ A list of objects, where each object in the list contains a
+ reference to its successor (for example, the successor of a commit
+ could be one of its parents).
+</dd><dt><span class="term">
+changeset
+</span></dt><dd>
+ BitKeeper/cvsps speak for "commit". Since git does not store
+ changes, but states, it really does not make sense to use
+ the term "changesets" with git.
+</dd><dt><span class="term">
+checkout
+</span></dt><dd>
+ The action of updating the working tree to a revision which was
+ stored in the object database.
+</dd><dt><span class="term">
+cherry-picking
+</span></dt><dd>
+ In SCM jargon, "cherry pick" means to choose a subset of
+ changes out of a series of changes (typically commits)
+ and record them as a new series of changes on top of
+ different codebase. In GIT, this is performed by
+ "git cherry-pick" command to extract the change
+ introduced by an existing commit and to record it based
+ on the tip of the current branch as a new commit.
+</dd><dt><span class="term">
+clean
+</span></dt><dd>
+ A working tree is clean, if it corresponds to the revision
+ referenced by the current head. Also see "dirty".
+</dd><dt><span class="term">
+commit
+</span></dt><dd>
+ As a verb: The action of storing the current state of the index in the
+ object database. The result is a revision.
+ As a noun: Short hand for commit object.
+</dd><dt><span class="term">
+commit object
+</span></dt><dd>
+ An object which contains the information about a particular
+ revision, such as parents, committer, author, date and the
+ tree object which corresponds to the top directory of the
+ stored revision.
+</dd><dt><span class="term">
+core git
+</span></dt><dd>
+ Fundamental data structures and utilities of git. Exposes only
+ limited source code management tools.
+</dd><dt><span class="term">
+DAG
+</span></dt><dd>
+ Directed acyclic graph. The commit objects form a directed acyclic
+ graph, because they have parents (directed), and the graph of commit
+ objects is acyclic (there is no chain which begins and ends with the
+ same object).
+</dd><dt><span class="term">
+dircache
+</span></dt><dd>
+ You are <span class="strong"><strong>waaaaay</strong></span> behind.
+</dd><dt><span class="term">
+dirty
+</span></dt><dd>
+ A working tree is said to be dirty if it contains modifications
+ which have not been committed to the current branch.
+</dd><dt><span class="term">
+directory
+</span></dt><dd>
+ The list you get with "ls" :-)
+</dd><dt><span class="term">
+ent
+</span></dt><dd>
+ Favorite synonym to "tree-ish" by some total geeks. See
+ <code class="literal">http://en.wikipedia.org/wiki/Ent_(Middle-earth)</code> for an in-depth
+ explanation. Avoid this term, not to confuse people.
+</dd><dt><span class="term">
+fast forward
+</span></dt><dd>
+ A fast-forward is a special type of merge where you have
+ a revision and you are "merging" another branch's changes
+ that happen to be a descendant of what you have.
+ In such these cases, you do not make a new merge commit but
+ instead just update to his revision. This will happen
+ frequently on a tracking branch of a remote repository.
+</dd><dt><span class="term">
+fetch
+</span></dt><dd>
+ Fetching a branch means to get the branch's head ref from a
+ remote repository, to find out which objects are missing from
+ the local object database, and to get them, too.
+</dd><dt><span class="term">
+file system
+</span></dt><dd>
+ Linus Torvalds originally designed git to be a user space file
+ system, i.e. the infrastructure to hold files and directories.
+ That ensured the efficiency and speed of git.
+</dd><dt><span class="term">
+git archive
+</span></dt><dd>
+ Synonym for repository (for arch people).
+</dd><dt><span class="term">
+grafts
+</span></dt><dd>
+ Grafts enables two otherwise different lines of development to be
+ joined together by recording fake ancestry information for commits.
+ This way you can make git pretend the set of parents a commit
+ has is different from what was recorded when the commit was created.
+ Configured via the <code class="literal">.git/info/grafts</code> file.
+</dd><dt><span class="term">
+hash
+</span></dt><dd>
+ In git's context, synonym to object name.
+</dd><dt><span class="term">
+head
+</span></dt><dd>
+ The top of a branch. It contains a ref to the corresponding
+ commit object.
+</dd><dt><span class="term">
+head ref
+</span></dt><dd>
+ A ref pointing to a head. Often, this is abbreviated to "head".
+ Head refs are stored in <code class="literal">$GIT_DIR/refs/heads/</code>.
+</dd><dt><span class="term">
+hook
+</span></dt><dd>
+ During the normal execution of several git commands,
+ call-outs are made to optional scripts that allow
+ a developer to add functionality or checking.
+ Typically, the hooks allow for a command to be pre-verified
+ and potentially aborted, and allow for a post-notification
+ after the operation is done.
+ The hook scripts are found in the <code class="literal">$GIT_DIR/hooks/</code> directory,
+ and are enabled by simply making them executable.
+</dd><dt><span class="term">
+index
+</span></dt><dd>
+ A collection of files with stat information, whose contents are
+ stored as objects. The index is a stored version of your working
+ tree. Truth be told, it can also contain a second, and even a third
+ version of a working tree, which are used when merging.
+</dd><dt><span class="term">
+index entry
+</span></dt><dd>
+ The information regarding a particular file, stored in the index.
+ An index entry can be unmerged, if a merge was started, but not
+ yet finished (i.e. if the index contains multiple versions of
+ that file).
+</dd><dt><span class="term">
+master
+</span></dt><dd>
+ The default development branch. Whenever you create a git
+ repository, a branch named "master" is created, and becomes
+ the active branch. In most cases, this contains the local
+ development, though that is purely conventional and not required.
+</dd><dt><span class="term">
+merge
+</span></dt><dd>
+ To merge branches means to try to accumulate the changes since a
+ common ancestor and apply them to the first branch. An automatic
+ merge uses heuristics to accomplish that. Evidently, an automatic
+ merge can fail.
+</dd><dt><span class="term">
+object
+</span></dt><dd>
+ The unit of storage in git. It is uniquely identified by
+ the SHA1 of its contents. Consequently, an object can not
+ be changed.
+</dd><dt><span class="term">
+object database
+</span></dt><dd>
+ Stores a set of "objects", and an individual object is identified
+ by its object name. The objects usually live in <code class="literal">$GIT_DIR/objects/</code>.
+</dd><dt><span class="term">
+object identifier
+</span></dt><dd>
+ Synonym for object name.
+</dd><dt><span class="term">
+object name
+</span></dt><dd>
+ The unique identifier of an object. The hash of the object's contents
+ using the Secure Hash Algorithm 1 and usually represented by the 40
+ character hexadecimal encoding of the hash of the object (possibly
+ followed by a white space).
+</dd><dt><span class="term">
+object type
+</span></dt><dd>
+ One of the identifiers "commit","tree","tag" and "blob" describing
+ the type of an object.
+</dd><dt><span class="term">
+octopus
+</span></dt><dd>
+ To merge more than two branches. Also denotes an intelligent
+ predator.
+</dd><dt><span class="term">
+origin
+</span></dt><dd>
+ The default upstream repository. Most projects have at
+ least one upstream project which they track. By default
+ <span class="emphasis"><em>origin</em></span> is used for that purpose. New upstream updates
+ will be fetched into remote tracking branches named
+ origin/name-of-upstream-branch, which you can see using
+ "git branch -r".
+</dd><dt><span class="term">
+pack
+</span></dt><dd>
+ A set of objects which have been compressed into one file (to save
+ space or to transmit them efficiently).
+</dd><dt><span class="term">
+pack index
+</span></dt><dd>
+ The list of identifiers, and other information, of the objects in a
+ pack, to assist in efficiently accessing the contents of a pack.
+</dd><dt><span class="term">
+parent
+</span></dt><dd>
+ A commit object contains a (possibly empty) list of the logical
+ predecessor(s) in the line of development, i.e. its parents.
+</dd><dt><span class="term">
+pickaxe
+</span></dt><dd>
+ The term pickaxe refers to an option to the diffcore routines
+ that help select changes that add or delete a given text string.
+ With the —pickaxe-all option, it can be used to view the
+ full changeset that introduced or removed, say, a particular
+ line of text. See <a href="git-diff.html" target="_top">git-diff(1)</a>.
+</dd><dt><span class="term">
+plumbing
+</span></dt><dd>
+ Cute name for core git.
+</dd><dt><span class="term">
+porcelain
+</span></dt><dd>
+ Cute name for programs and program suites depending on core git,
+ presenting a high level access to core git. Porcelains expose
+ more of a SCM interface than the plumbing.
+</dd><dt><span class="term">
+pull
+</span></dt><dd>
+ Pulling a branch means to fetch it and merge it.
+</dd><dt><span class="term">
+push
+</span></dt><dd>
+ Pushing a branch means to get the branch's head ref from a remote
+ repository, find out if it is an ancestor to the branch's local
+ head ref is a direct, and in that case, putting all objects, which
+ are reachable from the local head ref, and which are missing from
+ the remote repository, into the remote object database, and updating
+ the remote head ref. If the remote head is not an ancestor to the
+ local head, the push fails.
+</dd><dt><span class="term">
+reachable
+</span></dt><dd>
+ All of the ancestors of a given commit are said to be reachable from
+ that commit. More generally, one object is reachable from another if
+ we can reach the one from the other by a chain that follows tags to
+ whatever they tag, commits to their parents or trees, and trees to the
+ trees or blobs that they contain.
+</dd><dt><span class="term">
+rebase
+</span></dt><dd>
+ To clean a branch by starting from the head of the main line of
+ development ("master"), and reapply the (possibly cherry-picked)
+ changes from that branch.
+</dd><dt><span class="term">
+ref
+</span></dt><dd>
+ A 40-byte hex representation of a SHA1 or a name that denotes
+ a particular object. These may be stored in <code class="literal">$GIT_DIR/refs/</code>.
+</dd><dt><span class="term">
+refspec
+</span></dt><dd>
+ A refspec is used by fetch and push to describe the mapping
+ between remote ref and local ref. They are combined with
+ a colon in the format <src>:<dst>, preceded by an optional
+ plus sign, +. For example:
+ <code class="literal">git fetch $URL refs/heads/master:refs/heads/origin</code>
+ means "grab the master branch head from the $URL and store
+ it as my origin branch head".
+ And <code class="literal">git push $URL refs/heads/master:refs/heads/to-upstream</code>
+ means "publish my master branch head as to-upstream branch
+ at $URL". See also <a href="git-push.html" target="_top">git-push(1)</a>
+</dd><dt><span class="term">
+repository
+</span></dt><dd>
+ A collection of refs together with an object database containing
+ all objects, which are reachable from the refs, possibly accompanied
+ by meta data from one or more porcelains. A repository can
+ share an object database with other repositories.
+</dd><dt><span class="term">
+resolve
+</span></dt><dd>
+ The action of fixing up manually what a failed automatic merge
+ left behind.
+</dd><dt><span class="term">
+revision
+</span></dt><dd>
+ A particular state of files and directories which was stored in
+ the object database. It is referenced by a commit object.
+</dd><dt><span class="term">
+rewind
+</span></dt><dd>
+ To throw away part of the development, i.e. to assign the head to
+ an earlier revision.
+</dd><dt><span class="term">
+SCM
+</span></dt><dd>
+ Source code management (tool).
+</dd><dt><span class="term">
+SHA1
+</span></dt><dd>
+ Synonym for object name.
+</dd><dt><span class="term">
+shallow repository
+</span></dt><dd>
+ A shallow repository has an incomplete history some of
+ whose commits have parents cauterized away (in other
+ words, git is told to pretend that these commits do not
+ have the parents, even though they are recorded in the
+ commit object). This is sometimes useful when you are
+ interested only in the recent history of a project even
+ though the real history recorded in the upstream is
+ much larger. A shallow repository is created by giving
+ <code class="literal">—depth</code> option to <a href="git-clone.html" target="_top">git-clone(1)</a>, and its
+ history can be later deepened with <a href="git-fetch.html" target="_top">git-fetch(1)</a>.
+</dd><dt><span class="term">
+symref
+</span></dt><dd>
+ Symbolic reference: instead of containing the SHA1 id itself, it
+ is of the format <span class="emphasis"><em>ref: refs/some/thing</em></span> and when referenced, it
+ recursively dereferences to this reference. <span class="emphasis"><em>HEAD</em></span> is a prime
+ example of a symref. Symbolic references are manipulated with
+ the <a href="git-symbolic-ref.html" target="_top">git-symbolic-ref(1)</a> command.
+</dd><dt><span class="term">
+topic branch
+</span></dt><dd>
+ A regular git branch that is used by a developer to
+ identify a conceptual line of development. Since branches
+ are very easy and inexpensive, it is often desirable to
+ have several small branches that each contain very well
+ defined concepts or small incremental yet related changes.
+</dd><dt><span class="term">
+tracking branch
+</span></dt><dd>
+ A regular git branch that is used to follow changes from
+ another repository. A tracking branch should not contain
+ direct modifications or have local commits made to it.
+ A tracking branch can usually be identified as the
+ right-hand-side ref in a Pull: refspec.
+</dd><dt><span class="term">
+tree object
+</span></dt><dd>
+ An object containing a list of file names and modes along with refs
+ to the associated blob and/or tree objects. A tree is equivalent
+ to a directory.
+</dd><dt><span class="term">
+tree
+</span></dt><dd>
+ Either a working tree, or a tree object together with the
+ dependent blob and tree objects (i.e. a stored representation
+ of a working tree).
+</dd><dt><span class="term">
+tree-ish
+</span></dt><dd>
+ A ref pointing to either a commit object, a tree object, or a
+ tag object pointing to a tag or commit or tree object.
+</dd><dt><span class="term">
+tag object
+</span></dt><dd>
+ An object containing a ref pointing to another object, which can
+ contain a message just like a commit object. It can also
+ contain a (PGP) signature, in which case it is called a "signed
+ tag object".
+</dd><dt><span class="term">
+tag
+</span></dt><dd>
+ A ref pointing to a tag or commit object. In contrast to a head,
+ a tag is not changed by a commit. Tags (not tag objects) are
+ stored in <code class="literal">$GIT_DIR/refs/tags/</code>. A git tag has nothing to do with
+ a Lisp tag (which is called object type in git's context).
+ A tag is most typically used to mark a particular point in the
+ commit ancestry chain.
+</dd><dt><span class="term">
+unmerged index
+</span></dt><dd>
+ An index which contains unmerged index entries.
+</dd><dt><span class="term">
+working tree
+</span></dt><dd>
+ The set of files and directories currently being worked on,
+ i.e. you can work in your working tree without using git at all.
+</dd></dl></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id279940"></a>Chapter 10. Notes and todo list for this manual</h2></div></div></div><p>This is a work in progress.</p><p>The basic requirements:
+ - It must be readable in order, from beginning to end, by
+ someone intelligent with a basic grasp of the unix
+ commandline, but without any special knowledge of git. If
+ necessary, any other prerequisites should be specifically
+ mentioned as they arise.
+ - Whenever possible, section headings should clearly describe
+ the task they explain how to do, in language that requires
+ no more knowledge than necessary: for example, "importing
+ patches into a project" rather than "the git-am command"</p><p>Think about how to create a clear chapter dependency graph that will
+allow people to get to important topics without necessarily reading
+everything in between.</p><p>Scan Documentation/ for other stuff left out; in particular:
+ howto's
+ some of technical/?
+ hooks
+ list of commands in <a href="git.html" target="_top">git(1)</a></p><p>Scan email archives for other stuff left out</p><p>Scan man pages to see if any assume more background than this manual
+provides.</p><p>Simplify beginning by suggesting disconnected head instead of
+temporary branch creation?</p><p>Explain how to refer to file stages in the "how to resolve a merge"
+section: diff -1, -2, -3, —ours, —theirs :1:/path notation. The
+"git ls-files —unmerged —stage" thing is sorta useful too,
+actually. And note gitk —merge.</p><p>Add more good examples. Entire sections of just cookbook examples
+might be a good idea; maybe make an "advanced examples" section a
+standard end-of-chapter section?</p><p>Include cross-references to the glossary, where appropriate.</p><p>Document shallow clones? See draft 1.5.0 release notes for some
+documentation.</p><p>Add a sectin on working with other version control systems, including
+CVS, Subversion, and just imports of series of release tarballs.</p><p>More details on gitweb?</p><p>Write a chapter on using plumbing and writing scripts.</p></div></div></body></html>
--- /dev/null
+Git User's Manual
+_________________
+
+This manual is designed to be readable by someone with basic unix
+commandline skills, but no previous knowledge of git.
+
+Chapter 1 gives a brief overview of git commands, without any
+explanation; you may prefer to skip to chapter 2 on a first reading.
+
+Chapters 2 and 3 explain how to fetch and study a project using
+git--the tools you'd need to build and test a particular version of a
+software project, to search for regressions, and so on.
+
+Chapter 4 explains how to do development with git, and chapter 5 how
+to share that development with others.
+
+Further chapters cover more specialized topics.
+
+Comprehensive reference documentation is available through the man
+pages. For a command such as "git clone", just use
+
+------------------------------------------------
+$ man git-clone
+------------------------------------------------
+
+Git Quick Start
+===============
+
+This is a quick summary of the major commands; the following chapters
+will explain how these work in more detail.
+
+Creating a new repository
+-------------------------
+
+From a tarball:
+
+-----------------------------------------------
+$ tar xzf project.tar.gz
+$ cd project
+$ git init
+Initialized empty Git repository in .git/
+$ git add .
+$ git commit
+-----------------------------------------------
+
+From a remote repository:
+
+-----------------------------------------------
+$ git clone git://example.com/pub/project.git
+$ cd project
+-----------------------------------------------
+
+Managing branches
+-----------------
+
+-----------------------------------------------
+$ git branch # list all branches in this repo
+$ git checkout test # switch working directory to branch "test"
+$ git branch new # create branch "new" starting at current HEAD
+$ git branch -d new # delete branch "new"
+-----------------------------------------------
+
+Instead of basing new branch on current HEAD (the default), use:
+
+-----------------------------------------------
+$ git branch new test # branch named "test"
+$ git branch new v2.6.15 # tag named v2.6.15
+$ git branch new HEAD^ # commit before the most recent
+$ git branch new HEAD^^ # commit before that
+$ git branch new test~10 # ten commits before tip of branch "test"
+-----------------------------------------------
+
+Create and switch to a new branch at the same time:
+
+-----------------------------------------------
+$ git checkout -b new v2.6.15
+-----------------------------------------------
+
+Update and examine branches from the repository you cloned from:
+
+-----------------------------------------------
+$ git fetch # update
+$ git branch -r # list
+ origin/master
+ origin/next
+ ...
+$ git branch checkout -b masterwork origin/master
+-----------------------------------------------
+
+Fetch a branch from a different repository, and give it a new
+name in your repository:
+
+-----------------------------------------------
+$ git fetch git://example.com/project.git theirbranch:mybranch
+$ git fetch git://example.com/project.git v2.6.15:mybranch
+-----------------------------------------------
+
+Keep a list of repositories you work with regularly:
+
+-----------------------------------------------
+$ git remote add example git://example.com/project.git
+$ git remote # list remote repositories
+example
+origin
+$ git remote show example # get details
+* remote example
+ URL: git://example.com/project.git
+ Tracked remote branches
+ master next ...
+$ git fetch example # update branches from example
+$ git branch -r # list all remote branches
+-----------------------------------------------
+
+
+Exploring history
+-----------------
+
+-----------------------------------------------
+$ gitk # visualize and browse history
+$ git log # list all commits
+$ git log src/ # ...modifying src/
+$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
+$ git log master..test # ...in branch test, not in branch master
+$ git log test..master # ...in branch master, but not in test
+$ git log test...master # ...in one branch, not in both
+$ git log -S'foo()' # ...where difference contain "foo()"
+$ git log --since="2 weeks ago"
+$ git log -p # show patches as well
+$ git show # most recent commit
+$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
+$ git diff v2.6.15..HEAD # diff with current head
+$ git grep "foo()" # search working directory for "foo()"
+$ git grep v2.6.15 "foo()" # search old tree for "foo()"
+$ git show v2.6.15:a.txt # look at old version of a.txt
+-----------------------------------------------
+
+Search for regressions:
+
+-----------------------------------------------
+$ git bisect start
+$ git bisect bad # current version is bad
+$ git bisect good v2.6.13-rc2 # last known good revision
+Bisecting: 675 revisions left to test after this
+ # test here, then:
+$ git bisect good # if this revision is good, or
+$ git bisect bad # if this revision is bad.
+ # repeat until done.
+-----------------------------------------------
+
+Making changes
+--------------
+
+Make sure git knows who to blame:
+
+------------------------------------------------
+$ cat >~/.gitconfig <<\EOF
+[user]
+name = Your Name Comes Here
+email = you@yourdomain.example.com
+EOF
+------------------------------------------------
+
+Select file contents to include in the next commit, then make the
+commit:
+
+-----------------------------------------------
+$ git add a.txt # updated file
+$ git add b.txt # new file
+$ git rm c.txt # old file
+$ git commit
+-----------------------------------------------
+
+Or, prepare and create the commit in one step:
+
+-----------------------------------------------
+$ git commit d.txt # use latest content only of d.txt
+$ git commit -a # use latest content of all tracked files
+-----------------------------------------------
+
+Merging
+-------
+
+-----------------------------------------------
+$ git merge test # merge branch "test" into the current branch
+$ git pull git://example.com/project.git master
+ # fetch and merge in remote branch
+$ git pull . test # equivalent to git merge test
+-----------------------------------------------
+
+Sharing your changes
+--------------------
+
+Importing or exporting patches:
+
+-----------------------------------------------
+$ git format-patch origin..HEAD # format a patch for each commit
+ # in HEAD but not in origin
+$ git-am mbox # import patches from the mailbox "mbox"
+-----------------------------------------------
+
+Fetch a branch in a different git repository, then merge into the
+current branch:
+
+-----------------------------------------------
+$ git pull git://example.com/project.git theirbranch
+-----------------------------------------------
+
+Store the fetched branch into a local branch before merging into the
+current branch:
+
+-----------------------------------------------
+$ git pull git://example.com/project.git theirbranch:mybranch
+-----------------------------------------------
+
+After creating commits on a local branch, update the remote
+branch with your commits:
+
+-----------------------------------------------
+$ git push ssh://example.com/project.git mybranch:theirbranch
+-----------------------------------------------
+
+When remote and local branch are both named "test":
+
+-----------------------------------------------
+$ git push ssh://example.com/project.git test
+-----------------------------------------------
+
+Shortcut version for a frequently used remote repository:
+
+-----------------------------------------------
+$ git remote add example ssh://example.com/project.git
+$ git push example test
+-----------------------------------------------
+
+Repository maintenance
+----------------------
+
+Check for corruption:
+
+-----------------------------------------------
+$ git fsck
+-----------------------------------------------
+
+Recompress, remove unused cruft:
+
+-----------------------------------------------
+$ git gc
+-----------------------------------------------
+
+Repositories and Branches
+=========================
+
+How to get a git repository
+---------------------------
+
+It will be useful to have a git repository to experiment with as you
+read this manual.
+
+The best way to get one is by using the gitlink:git-clone[1] command
+to download a copy of an existing repository for a project that you
+are interested in. If you don't already have a project in mind, here
+are some interesting examples:
+
+------------------------------------------------
+ # git itself (approx. 10MB download):
+$ git clone git://git.kernel.org/pub/scm/git/git.git
+ # the linux kernel (approx. 150MB download):
+$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git
+------------------------------------------------
+
+The initial clone may be time-consuming for a large project, but you
+will only need to clone once.
+
+The clone command creates a new directory named after the project
+("git" or "linux-2.6" in the examples above). After you cd into this
+directory, you will see that it contains a copy of the project files,
+together with a special top-level directory named ".git", which
+contains all the information about the history of the project.
+
+In most of the following, examples will be taken from one of the two
+repositories above.
+
+How to check out a different version of a project
+-------------------------------------------------
+
+Git is best thought of as a tool for storing the history of a
+collection of files. It stores the history as a compressed
+collection of interrelated snapshots (versions) of the project's
+contents.
+
+A single git repository may contain multiple branches. Each branch
+is a bookmark referencing a particular point in the project history.
+The gitlink:git-branch[1] command shows you the list of branches:
+
+------------------------------------------------
+$ git branch
+* master
+------------------------------------------------
+
+A freshly cloned repository contains a single branch, named "master",
+and the working directory contains the version of the project
+referred to by the master branch.
+
+Most projects also use tags. Tags, like branches, are references
+into the project's history, and can be listed using the
+gitlink:git-tag[1] command:
+
+------------------------------------------------
+$ git tag -l
+v2.6.11
+v2.6.11-tree
+v2.6.12
+v2.6.12-rc2
+v2.6.12-rc3
+v2.6.12-rc4
+v2.6.12-rc5
+v2.6.12-rc6
+v2.6.13
+...
+------------------------------------------------
+
+Tags are expected to always point at the same version of a project,
+while branches are expected to advance as development progresses.
+
+Create a new branch pointing to one of these versions and check it
+out using gitlink:git-checkout[1]:
+
+------------------------------------------------
+$ git checkout -b new v2.6.13
+------------------------------------------------
+
+The working directory then reflects the contents that the project had
+when it was tagged v2.6.13, and gitlink:git-branch[1] shows two
+branches, with an asterisk marking the currently checked-out branch:
+
+------------------------------------------------
+$ git branch
+ master
+* new
+------------------------------------------------
+
+If you decide that you'd rather see version 2.6.17, you can modify
+the current branch to point at v2.6.17 instead, with
+
+------------------------------------------------
+$ git reset --hard v2.6.17
+------------------------------------------------
+
+Note that if the current branch was your only reference to a
+particular point in history, then resetting that branch may leave you
+with no way to find the history it used to point to; so use this
+command carefully.
+
+Understanding History: Commits
+------------------------------
+
+Every change in the history of a project is represented by a commit.
+The gitlink:git-show[1] command shows the most recent commit on the
+current branch:
+
+------------------------------------------------
+$ git show
+commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2
+Author: Jamal Hadi Salim <hadi@cyberus.ca>
+Date: Sat Dec 2 22:22:25 2006 -0800
+
+ [XFRM]: Fix aevent structuring to be more complete.
+
+ aevents can not uniquely identify an SA. We break the ABI with this
+ patch, but consensus is that since it is not yet utilized by any
+ (known) application then it is fine (better do it now than later).
+
+ Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
+ Signed-off-by: David S. Miller <davem@davemloft.net>
+
+diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt
+index 8be626f..d7aac9d 100644
+--- a/Documentation/networking/xfrm_sync.txt
++++ b/Documentation/networking/xfrm_sync.txt
+@@ -47,10 +47,13 @@ aevent_id structure looks like:
+
+ struct xfrm_aevent_id {
+ struct xfrm_usersa_id sa_id;
++ xfrm_address_t saddr;
+ __u32 flags;
++ __u32 reqid;
+ };
+...
+------------------------------------------------
+
+As you can see, a commit shows who made the latest change, what they
+did, and why.
+
+Every commit has a 40-hexdigit id, sometimes called the "object name"
+or the "SHA1 id", shown on the first line of the "git show" output.
+You can usually refer to a commit by a shorter name, such as a tag or a
+branch name, but this longer name can also be useful. Most
+importantly, it is a globally unique name for this commit: so if you
+tell somebody else the object name (for example in email), then you are
+guaranteed that name will refer to the same commit in their repository
+that you it does in yours (assuming their repository has that commit at
+all).
+
+Understanding history: commits, parents, and reachability
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Every commit (except the very first commit in a project) also has a
+parent commit which shows what happened before this commit.
+Following the chain of parents will eventually take you back to the
+beginning of the project.
+
+However, the commits do not form a simple list; git allows lines of
+development to diverge and then reconverge, and the point where two
+lines of development reconverge is called a "merge". The commit
+representing a merge can therefore have more than one parent, with
+each parent representing the most recent commit on one of the lines
+of development leading to that point.
+
+The best way to see how this works is using the gitlink:gitk[1]
+command; running gitk now on a git repository and looking for merge
+commits will help understand how the git organizes history.
+
+In the following, we say that commit X is "reachable" from commit Y
+if commit X is an ancestor of commit Y. Equivalently, you could say
+that Y is a descendent of X, or that there is a chain of parents
+leading from commit Y to commit X.
+
+Undestanding history: History diagrams
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+We will sometimes represent git history using diagrams like the one
+below. Commits are shown as "o", and the links between them with
+lines drawn with - / and \. Time goes left to right:
+
+ o--o--o <-- Branch A
+ /
+ o--o--o <-- master
+ \
+ o--o--o <-- Branch B
+
+If we need to talk about a particular commit, the character "o" may
+be replaced with another letter or number.
+
+Understanding history: What is a branch?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Though we've been using the word "branch" to mean a kind of reference
+to a particular commit, the word branch is also commonly used to
+refer to the line of commits leading up to that point. In the
+example above, git may think of the branch named "A" as just a
+pointer to one particular commit, but we may refer informally to the
+line of three commits leading up to that point as all being part of
+"branch A".
+
+If we need to make it clear that we're just talking about the most
+recent commit on the branch, we may refer to that commit as the
+"head" of the branch.
+
+Manipulating branches
+---------------------
+
+Creating, deleting, and modifying branches is quick and easy; here's
+a summary of the commands:
+
+git branch::
+ list all branches
+git branch <branch>::
+ create a new branch named <branch>, referencing the same
+ point in history as the current branch
+git branch <branch> <start-point>::
+ create a new branch named <branch>, referencing
+ <start-point>, which may be specified any way you like,
+ including using a branch name or a tag name
+git branch -d <branch>::
+ delete the branch <branch>; if the branch you are deleting
+ points to a commit which is not reachable from this branch,
+ this command will fail with a warning.
+git branch -D <branch>::
+ even if the branch points to a commit not reachable
+ from the current branch, you may know that that commit
+ is still reachable from some other branch or tag. In that
+ case it is safe to use this command to force git to delete
+ the branch.
+git checkout <branch>::
+ make the current branch <branch>, updating the working
+ directory to reflect the version referenced by <branch>
+git checkout -b <new> <start-point>::
+ create a new branch <new> referencing <start-point>, and
+ check it out.
+
+It is also useful to know that the special symbol "HEAD" can always
+be used to refer to the current branch.
+
+Examining branches from a remote repository
+-------------------------------------------
+
+The "master" branch that was created at the time you cloned is a copy
+of the HEAD in the repository that you cloned from. That repository
+may also have had other branches, though, and your local repository
+keeps branches which track each of those remote branches, which you
+can view using the "-r" option to gitlink:git-branch[1]:
+
+------------------------------------------------
+$ git branch -r
+ origin/HEAD
+ origin/html
+ origin/maint
+ origin/man
+ origin/master
+ origin/next
+ origin/pu
+ origin/todo
+------------------------------------------------
+
+You cannot check out these remote-tracking branches, but you can
+examine them on a branch of your own, just as you would a tag:
+
+------------------------------------------------
+$ git checkout -b my-todo-copy origin/todo
+------------------------------------------------
+
+Note that the name "origin" is just the name that git uses by default
+to refer to the repository that you cloned from.
+
+[[how-git-stores-references]]
+Naming branches, tags, and other references
+-------------------------------------------
+
+Branches, remote-tracking branches, and tags are all references to
+commits. All references are named with a slash-separated path name
+starting with "refs"; the names we've been using so far are actually
+shorthand:
+
+ - The branch "test" is short for "refs/heads/test".
+ - The tag "v2.6.18" is short for "refs/tags/v2.6.18".
+ - "origin/master" is short for "refs/remotes/origin/master".
+
+The full name is occasionally useful if, for example, there ever
+exists a tag and a branch with the same name.
+
+As another useful shortcut, if the repository "origin" posesses only
+a single branch, you can refer to that branch as just "origin".
+
+More generally, if you have defined a remote repository named
+"example", you can refer to the branch in that repository as
+"example". And for a repository with multiple branches, this will
+refer to the branch designated as the "HEAD" branch.
+
+For the complete list of paths which git checks for references, and
+the order it uses to decide which to choose when there are multiple
+references with the same shorthand name, see the "SPECIFYING
+REVISIONS" section of gitlink:git-rev-parse[1].
+
+[[Updating-a-repository-with-git-fetch]]
+Updating a repository with git fetch
+------------------------------------
+
+Eventually the developer cloned from will do additional work in her
+repository, creating new commits and advancing the branches to point
+at the new commits.
+
+The command "git fetch", with no arguments, will update all of the
+remote-tracking branches to the latest version found in her
+repository. It will not touch any of your own branches--not even the
+"master" branch that was created for you on clone.
+
+Fetching branches from other repositories
+-----------------------------------------
+
+You can also track branches from repositories other than the one you
+cloned from, using gitlink:git-remote[1]:
+
+-------------------------------------------------
+$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
+$ git fetch
+* refs/remotes/linux-nfs/master: storing branch 'master' ...
+ commit: bf81b46
+-------------------------------------------------
+
+New remote-tracking branches will be stored under the shorthand name
+that you gave "git remote add", in this case linux-nfs:
+
+-------------------------------------------------
+$ git branch -r
+linux-nfs/master
+origin/master
+-------------------------------------------------
+
+If you run "git fetch <remote>" later, the tracking branches for the
+named <remote> will be updated.
+
+If you examine the file .git/config, you will see that git has added
+a new stanza:
+
+-------------------------------------------------
+$ cat .git/config
+...
+[remote "linux-nfs"]
+ url = git://linux-nfs.org/~bfields/git.git
+ fetch = +refs/heads/*:refs/remotes/linux-nfs-read/*
+...
+-------------------------------------------------
+
+This is what causes git to track the remote's branches; you may modify
+or delete these configuration options by editing .git/config with a
+text editor. (See the "CONFIGURATION FILE" section of
+gitlink:git-config[1] for details.)
+
+Exploring git history
+=====================
+
+Git is best thought of as a tool for storing the history of a
+collection of files. It does this by storing compressed snapshots of
+the contents of a file heirarchy, together with "commits" which show
+the relationships between these snapshots.
+
+Git provides extremely flexible and fast tools for exploring the
+history of a project.
+
+We start with one specialized tool which is useful for finding the
+commit that introduced a bug into a project.
+
+How to use bisect to find a regression
+--------------------------------------
+
+Suppose version 2.6.18 of your project worked, but the version at
+"master" crashes. Sometimes the best way to find the cause of such a
+regression is to perform a brute-force search through the project's
+history to find the particular commit that caused the problem. The
+gitlink:git-bisect[1] command can help you do this:
+
+-------------------------------------------------
+$ git bisect start
+$ git bisect good v2.6.18
+$ git bisect bad master
+Bisecting: 3537 revisions left to test after this
+[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]
+-------------------------------------------------
+
+If you run "git branch" at this point, you'll see that git has
+temporarily moved you to a new branch named "bisect". This branch
+points to a commit (with commit id 65934...) that is reachable from
+v2.6.19 but not from v2.6.18. Compile and test it, and see whether
+it crashes. Assume it does crash. Then:
+
+-------------------------------------------------
+$ git bisect bad
+Bisecting: 1769 revisions left to test after this
+[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings
+-------------------------------------------------
+
+checks out an older version. Continue like this, telling git at each
+stage whether the version it gives you is good or bad, and notice
+that the number of revisions left to test is cut approximately in
+half each time.
+
+After about 13 tests (in this case), it will output the commit id of
+the guilty commit. You can then examine the commit with
+gitlink:git-show[1], find out who wrote it, and mail them your bug
+report with the commit id. Finally, run
+
+-------------------------------------------------
+$ git bisect reset
+-------------------------------------------------
+
+to return you to the branch you were on before and delete the
+temporary "bisect" branch.
+
+Note that the version which git-bisect checks out for you at each
+point is just a suggestion, and you're free to try a different
+version if you think it would be a good idea. For example,
+occasionally you may land on a commit that broke something unrelated;
+run
+
+-------------------------------------------------
+$ git bisect-visualize
+-------------------------------------------------
+
+which will run gitk and label the commit it chose with a marker that
+says "bisect". Chose a safe-looking commit nearby, note its commit
+id, and check it out with:
+
+-------------------------------------------------
+$ git reset --hard fb47ddb2db...
+-------------------------------------------------
+
+then test, run "bisect good" or "bisect bad" as appropriate, and
+continue.
+
+Naming commits
+--------------
+
+We have seen several ways of naming commits already:
+
+ - 40-hexdigit object name
+ - branch name: refers to the commit at the head of the given
+ branch
+ - tag name: refers to the commit pointed to by the given tag
+ (we've seen branches and tags are special cases of
+ <<how-git-stores-references,references>>).
+ - HEAD: refers to the head of the current branch
+
+There are many more; see the "SPECIFYING REVISIONS" section of the
+gitlink:git-rev-parse[1] man page for the complete list of ways to
+name revisions. Some examples:
+
+-------------------------------------------------
+$ git show fb47ddb2 # the first few characters of the object name
+ # are usually enough to specify it uniquely
+$ git show HEAD^ # the parent of the HEAD commit
+$ git show HEAD^^ # the grandparent
+$ git show HEAD~4 # the great-great-grandparent
+-------------------------------------------------
+
+Recall that merge commits may have more than one parent; by default,
+^ and ~ follow the first parent listed in the commit, but you can
+also choose:
+
+-------------------------------------------------
+$ git show HEAD^1 # show the first parent of HEAD
+$ git show HEAD^2 # show the second parent of HEAD
+-------------------------------------------------
+
+In addition to HEAD, there are several other special names for
+commits:
+
+Merges (to be discussed later), as well as operations such as
+git-reset, which change the currently checked-out commit, generally
+set ORIG_HEAD to the value HEAD had before the current operation.
+
+The git-fetch operation always stores the head of the last fetched
+branch in FETCH_HEAD. For example, if you run git fetch without
+specifying a local branch as the target of the operation
+
+-------------------------------------------------
+$ git fetch git://example.com/proj.git theirbranch
+-------------------------------------------------
+
+the fetched commits will still be available from FETCH_HEAD.
+
+When we discuss merges we'll also see the special name MERGE_HEAD,
+which refers to the other branch that we're merging in to the current
+branch.
+
+The gitlink:git-rev-parse[1] command is a low-level command that is
+occasionally useful for translating some name for a commit to the object
+name for that commit:
+
+-------------------------------------------------
+$ git rev-parse origin
+e05db0fd4f31dde7005f075a84f96b360d05984b
+-------------------------------------------------
+
+Creating tags
+-------------
+
+We can also create a tag to refer to a particular commit; after
+running
+
+-------------------------------------------------
+$ git-tag stable-1 1b2e1d63ff
+-------------------------------------------------
+
+You can use stable-1 to refer to the commit 1b2e1d63ff.
+
+This creates a "lightweight" tag. If the tag is a tag you wish to
+share with others, and possibly sign cryptographically, then you
+should create a tag object instead; see the gitlink:git-tag[1] man
+page for details.
+
+Browsing revisions
+------------------
+
+The gitlink:git-log[1] command can show lists of commits. On its
+own, it shows all commits reachable from the parent commit; but you
+can also make more specific requests:
+
+-------------------------------------------------
+$ git log v2.5.. # commits since (not reachable from) v2.5
+$ git log test..master # commits reachable from master but not test
+$ git log master..test # ...reachable from test but not master
+$ git log master...test # ...reachable from either test or master,
+ # but not both
+$ git log --since="2 weeks ago" # commits from the last 2 weeks
+$ git log Makefile # commits which modify Makefile
+$ git log fs/ # ... which modify any file under fs/
+$ git log -S'foo()' # commits which add or remove any file data
+ # matching the string 'foo()'
+-------------------------------------------------
+
+And of course you can combine all of these; the following finds
+commits since v2.5 which touch the Makefile or any file under fs:
+
+-------------------------------------------------
+$ git log v2.5.. Makefile fs/
+-------------------------------------------------
+
+You can also ask git log to show patches:
+
+-------------------------------------------------
+$ git log -p
+-------------------------------------------------
+
+See the "--pretty" option in the gitlink:git-log[1] man page for more
+display options.
+
+Note that git log starts with the most recent commit and works
+backwards through the parents; however, since git history can contain
+multiple independant lines of development, the particular order that
+commits are listed in may be somewhat arbitrary.
+
+Generating diffs
+----------------
+
+You can generate diffs between any two versions using
+gitlink:git-diff[1]:
+
+-------------------------------------------------
+$ git diff master..test
+-------------------------------------------------
+
+Sometimes what you want instead is a set of patches:
+
+-------------------------------------------------
+$ git format-patch master..test
+-------------------------------------------------
+
+will generate a file with a patch for each commit reachable from test
+but not from master. Note that if master also has commits which are
+not reachable from test, then the combined result of these patches
+will not be the same as the diff produced by the git-diff example.
+
+Viewing old file versions
+-------------------------
+
+You can always view an old version of a file by just checking out the
+correct revision first. But sometimes it is more convenient to be
+able to view an old version of a single file without checking
+anything out; this command does that:
+
+-------------------------------------------------
+$ git show v2.5:fs/locks.c
+-------------------------------------------------
+
+Before the colon may be anything that names a commit, and after it
+may be any path to a file tracked by git.
+
+Examples
+--------
+
+Check whether two branches point at the same history
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Suppose you want to check whether two branches point at the same point
+in history.
+
+-------------------------------------------------
+$ git diff origin..master
+-------------------------------------------------
+
+will tell you whether the contents of the project are the same at the
+two branches; in theory, however, it's possible that the same project
+contents could have been arrived at by two different historical
+routes. You could compare the object names:
+
+-------------------------------------------------
+$ git rev-list origin
+e05db0fd4f31dde7005f075a84f96b360d05984b
+$ git rev-list master
+e05db0fd4f31dde7005f075a84f96b360d05984b
+-------------------------------------------------
+
+Or you could recall that the ... operator selects all commits
+contained reachable from either one reference or the other but not
+both: so
+
+-------------------------------------------------
+$ git log origin...master
+-------------------------------------------------
+
+will return no commits when the two branches are equal.
+
+Find first tagged version including a given fix
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Suppose you know that the commit e05db0fd fixed a certain problem.
+You'd like to find the earliest tagged release that contains that
+fix.
+
+Of course, there may be more than one answer--if the history branched
+after commit e05db0fd, then there could be multiple "earliest" tagged
+releases.
+
+You could just visually inspect the commits since e05db0fd:
+
+-------------------------------------------------
+$ gitk e05db0fd..
+-------------------------------------------------
+
+Or you can use gitlink:git-name-rev[1], which will give the commit a
+name based on any tag it finds pointing to one of the commit's
+descendants:
+
+-------------------------------------------------
+$ git name-rev e05db0fd
+e05db0fd tags/v1.5.0-rc1^0~23
+-------------------------------------------------
+
+The gitlink:git-describe[1] command does the opposite, naming the
+revision using a tag on which the given commit is based:
+
+-------------------------------------------------
+$ git describe e05db0fd
+v1.5.0-rc0-ge05db0f
+-------------------------------------------------
+
+but that may sometimes help you guess which tags might come after the
+given commit.
+
+If you just want to verify whether a given tagged version contains a
+given commit, you could use gitlink:git-merge-base[1]:
+
+-------------------------------------------------
+$ git merge-base e05db0fd v1.5.0-rc1
+e05db0fd4f31dde7005f075a84f96b360d05984b
+-------------------------------------------------
+
+The merge-base command finds a common ancestor of the given commits,
+and always returns one or the other in the case where one is a
+descendant of the other; so the above output shows that e05db0fd
+actually is an ancestor of v1.5.0-rc1.
+
+Alternatively, note that
+
+-------------------------------------------------
+$ git log v1.5.0-rc1..e05db0fd
+-------------------------------------------------
+
+will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
+because it outputs only commits that are not reachable from v1.5.0-rc1.
+
+As yet another alternative, the gitlink:git-show-branch[1] command lists
+the commits reachable from its arguments with a display on the left-hand
+side that indicates which arguments that commit is reachable from. So,
+you can run something like
+
+-------------------------------------------------
+$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
+! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
+available
+ ! [v1.5.0-rc0] GIT v1.5.0 preview
+ ! [v1.5.0-rc1] GIT v1.5.0-rc1
+ ! [v1.5.0-rc2] GIT v1.5.0-rc2
+...
+-------------------------------------------------
+
+then search for a line that looks like
+
+-------------------------------------------------
++ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
+available
+-------------------------------------------------
+
+Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and
+from v1.5.0-rc2, but not from v1.5.0-rc0.
+
+
+Developing with git
+===================
+
+Telling git your name
+---------------------
+
+Before creating any commits, you should introduce yourself to git. The
+easiest way to do so is:
+
+------------------------------------------------
+$ cat >~/.gitconfig <<\EOF
+[user]
+ name = Your Name Comes Here
+ email = you@yourdomain.example.com
+EOF
+------------------------------------------------
+
+(See the "CONFIGURATION FILE" section of gitlink:git-config[1] for
+details on the configuration file.)
+
+
+Creating a new repository
+-------------------------
+
+Creating a new repository from scratch is very easy:
+
+-------------------------------------------------
+$ mkdir project
+$ cd project
+$ git init
+-------------------------------------------------
+
+If you have some initial content (say, a tarball):
+
+-------------------------------------------------
+$ tar -xzvf project.tar.gz
+$ cd project
+$ git init
+$ git add . # include everything below ./ in the first commit:
+$ git commit
+-------------------------------------------------
+
+[[how-to-make-a-commit]]
+how to make a commit
+--------------------
+
+Creating a new commit takes three steps:
+
+ 1. Making some changes to the working directory using your
+ favorite editor.
+ 2. Telling git about your changes.
+ 3. Creating the commit using the content you told git about
+ in step 2.
+
+In practice, you can interleave and repeat steps 1 and 2 as many
+times as you want: in order to keep track of what you want committed
+at step 3, git maintains a snapshot of the tree's contents in a
+special staging area called "the index."
+
+At the beginning, the content of the index will be identical to
+that of the HEAD. The command "git diff --cached", which shows
+the difference between the HEAD and the index, should therefore
+produce no output at that point.
+
+Modifying the index is easy:
+
+To update the index with the new contents of a modified file, use
+
+-------------------------------------------------
+$ git add path/to/file
+-------------------------------------------------
+
+To add the contents of a new file to the index, use
+
+-------------------------------------------------
+$ git add path/to/file
+-------------------------------------------------
+
+To remove a file from the index and from the working tree,
+
+-------------------------------------------------
+$ git rm path/to/file
+-------------------------------------------------
+
+After each step you can verify that
+
+-------------------------------------------------
+$ git diff --cached
+-------------------------------------------------
+
+always shows the difference between the HEAD and the index file--this
+is what you'd commit if you created the commit now--and that
+
+-------------------------------------------------
+$ git diff
+-------------------------------------------------
+
+shows the difference between the working tree and the index file.
+
+Note that "git add" always adds just the current contents of a file
+to the index; further changes to the same file will be ignored unless
+you run git-add on the file again.
+
+When you're ready, just run
+
+-------------------------------------------------
+$ git commit
+-------------------------------------------------
+
+and git will prompt you for a commit message and then create the new
+commmit. Check to make sure it looks like what you expected with
+
+-------------------------------------------------
+$ git show
+-------------------------------------------------
+
+As a special shortcut,
+
+-------------------------------------------------
+$ git commit -a
+-------------------------------------------------
+
+will update the index with any files that you've modified or removed
+and create a commit, all in one step.
+
+A number of commands are useful for keeping track of what you're
+about to commit:
+
+-------------------------------------------------
+$ git diff --cached # difference between HEAD and the index; what
+ # would be commited if you ran "commit" now.
+$ git diff # difference between the index file and your
+ # working directory; changes that would not
+ # be included if you ran "commit" now.
+$ git status # a brief per-file summary of the above.
+-------------------------------------------------
+
+creating good commit messages
+-----------------------------
+
+Though not required, it's a good idea to begin the commit message
+with a single short (less than 50 character) line summarizing the
+change, followed by a blank line and then a more thorough
+description. Tools that turn commits into email, for example, use
+the first line on the Subject line and the rest of the commit in the
+body.
+
+how to merge
+------------
+
+You can rejoin two diverging branches of development using
+gitlink:git-merge[1]:
+
+-------------------------------------------------
+$ git merge branchname
+-------------------------------------------------
+
+merges the development in the branch "branchname" into the current
+branch. If there are conflicts--for example, if the same file is
+modified in two different ways in the remote branch and the local
+branch--then you are warned; the output may look something like this:
+
+-------------------------------------------------
+$ git pull . next
+Trying really trivial in-index merge...
+fatal: Merge requires file-level merging
+Nope.
+Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086
+Merging:
+15e2162 world
+77976da goodbye
+found 1 common ancestor(s):
+d122ed4 initial
+Auto-merging file.txt
+CONFLICT (content): Merge conflict in file.txt
+Automatic merge failed; fix conflicts and then commit the result.
+-------------------------------------------------
+
+Conflict markers are left in the problematic files, and after
+you resolve the conflicts manually, you can update the index
+with the contents and run git commit, as you normally would when
+creating a new file.
+
+If you examine the resulting commit using gitk, you will see that it
+has two parents, one pointing to the top of the current branch, and
+one to the top of the other branch.
+
+In more detail:
+
+[[resolving-a-merge]]
+Resolving a merge
+-----------------
+
+When a merge isn't resolved automatically, git leaves the index and
+the working tree in a special state that gives you all the
+information you need to help resolve the merge.
+
+Files with conflicts are marked specially in the index, so until you
+resolve the problem and update the index, git commit will fail:
+
+-------------------------------------------------
+$ git commit
+file.txt: needs merge
+-------------------------------------------------
+
+Also, git status will list those files as "unmerged".
+
+All of the changes that git was able to merge automatically are
+already added to the index file, so gitlink:git-diff[1] shows only
+the conflicts. Also, it uses a somewhat unusual syntax:
+
+-------------------------------------------------
+$ git diff
+diff --cc file.txt
+index 802992c,2b60207..0000000
+--- a/file.txt
++++ b/file.txt
+@@@ -1,1 -1,1 +1,5 @@@
+++<<<<<<< HEAD:file.txt
+ +Hello world
+++=======
++ Goodbye
+++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt
+-------------------------------------------------
+
+Recall that the commit which will be commited after we resolve this
+conflict will have two parents instead of the usual one: one parent
+will be HEAD, the tip of the current branch; the other will be the
+tip of the other branch, which is stored temporarily in MERGE_HEAD.
+
+The diff above shows the differences between the working-tree version
+of file.txt and two previous version: one version from HEAD, and one
+from MERGE_HEAD. So instead of preceding each line by a single "+"
+or "-", it now uses two columns: the first column is used for
+differences between the first parent and the working directory copy,
+and the second for differences between the second parent and the
+working directory copy. Thus after resolving the conflict in the
+obvious way, the diff will look like:
+
+-------------------------------------------------
+$ git diff
+diff --cc file.txt
+index 802992c,2b60207..0000000
+--- a/file.txt
++++ b/file.txt
+@@@ -1,1 -1,1 +1,1 @@@
+- Hello world
+ -Goodbye
+++Goodbye world
+-------------------------------------------------
+
+This shows that our resolved version deleted "Hello world" from the
+first parent, deleted "Goodbye" from the second parent, and added
+"Goodbye world", which was previously absent from both.
+
+The gitlink:git-log[1] command also provides special help for merges:
+
+-------------------------------------------------
+$ git log --merge
+-------------------------------------------------
+
+This will list all commits which exist only on HEAD or on MERGE_HEAD,
+and which touch an unmerged file.
+
+We can now add the resolved version to the index and commit:
+
+-------------------------------------------------
+$ git add file.txt
+$ git commit
+-------------------------------------------------
+
+Note that the commit message will already be filled in for you with
+some information about the merge. Normally you can just use this
+default message unchanged, but you may add additional commentary of
+your own if desired.
+
+[[undoing-a-merge]]
+undoing a merge
+---------------
+
+If you get stuck and decide to just give up and throw the whole mess
+away, you can always return to the pre-merge state with
+
+-------------------------------------------------
+$ git reset --hard HEAD
+-------------------------------------------------
+
+Or, if you've already commited the merge that you want to throw away,
+
+-------------------------------------------------
+$ git reset --hard HEAD^
+-------------------------------------------------
+
+However, this last command can be dangerous in some cases--never
+throw away a commit you have already committed if that commit may
+itself have been merged into another branch, as doing so may confuse
+further merges.
+
+Fast-forward merges
+-------------------
+
+There is one special case not mentioned above, which is treated
+differently. Normally, a merge results in a merge commit, with two
+parents, one pointing at each of the two lines of development that
+were merged.
+
+However, if one of the two lines of development is completely
+contained within the other--so every commit present in the one is
+already contained in the other--then git just performs a
+<<fast-forwards,fast forward>>; the head of the current branch is
+moved forward to point at the head of the merged-in branch, without
+any new commits being created.
+
+Fixing mistakes
+---------------
+
+If you've messed up the working tree, but haven't yet committed your
+mistake, you can return the entire working tree to the last committed
+state with
+
+-------------------------------------------------
+$ git reset --hard HEAD
+-------------------------------------------------
+
+If you make a commit that you later wish you hadn't, there are two
+fundamentally different ways to fix the problem:
+
+ 1. You can create a new commit that undoes whatever was done
+ by the previous commit. This is the correct thing if your
+ mistake has already been made public.
+
+ 2. You can go back and modify the old commit. You should
+ never do this if you have already made the history public;
+ git does not normally expect the "history" of a project to
+ change, and cannot correctly perform repeated merges from
+ a branch that has had its history changed.
+
+Fixing a mistake with a new commit
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Creating a new commit that reverts an earlier change is very easy;
+just pass the gitlink:git-revert[1] command a reference to the bad
+commit; for example, to revert the most recent commit:
+
+-------------------------------------------------
+$ git revert HEAD
+-------------------------------------------------
+
+This will create a new commit which undoes the change in HEAD. You
+will be given a chance to edit the commit message for the new commit.
+
+You can also revert an earlier change, for example, the next-to-last:
+
+-------------------------------------------------
+$ git revert HEAD^
+-------------------------------------------------
+
+In this case git will attempt to undo the old change while leaving
+intact any changes made since then. If more recent changes overlap
+with the changes to be reverted, then you will be asked to fix
+conflicts manually, just as in the case of <<resolving-a-merge,
+resolving a merge>>.
+
+Fixing a mistake by editing history
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If the problematic commit is the most recent commit, and you have not
+yet made that commit public, then you may just
+<<undoing-a-merge,destroy it using git-reset>>.
+
+Alternatively, you
+can edit the working directory and update the index to fix your
+mistake, just as if you were going to <<how-to-make-a-commit,create a
+new commit>>, then run
+
+-------------------------------------------------
+$ git commit --amend
+-------------------------------------------------
+
+which will replace the old commit by a new commit incorporating your
+changes, giving you a chance to edit the old commit message first.
+
+Again, you should never do this to a commit that may already have
+been merged into another branch; use gitlink:git-revert[1] instead in
+that case.
+
+It is also possible to edit commits further back in the history, but
+this is an advanced topic to be left for
+<<cleaning-up-history,another chapter>>.
+
+Checking out an old version of a file
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In the process of undoing a previous bad change, you may find it
+useful to check out an older version of a particular file using
+gitlink:git-checkout[1]. We've used git checkout before to switch
+branches, but it has quite different behavior if it is given a path
+name: the command
+
+-------------------------------------------------
+$ git checkout HEAD^ path/to/file
+-------------------------------------------------
+
+replaces path/to/file by the contents it had in the commit HEAD^, and
+also updates the index to match. It does not change branches.
+
+If you just want to look at an old version of the file, without
+modifying the working directory, you can do that with
+gitlink:git-show[1]:
+
+-------------------------------------------------
+$ git show HEAD^ path/to/file
+-------------------------------------------------
+
+which will display the given version of the file.
+
+Ensuring good performance
+-------------------------
+
+On large repositories, git depends on compression to keep the history
+information from taking up to much space on disk or in memory.
+
+This compression is not performed automatically. Therefore you
+should occasionally run gitlink:git-gc[1]:
+
+-------------------------------------------------
+$ git gc
+-------------------------------------------------
+
+to recompress the archive. This can be very time-consuming, so
+you may prefer to run git-gc when you are not doing other work.
+
+Ensuring reliability
+--------------------
+
+Checking the repository for corruption
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The gitlink:git-fsck[1] command runs a number of self-consistency checks
+on the repository, and reports on any problems. This may take some
+time. The most common warning by far is about "dangling" objects:
+
+-------------------------------------------------
+$ git fsck
+dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
+dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
+dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
+dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
+dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
+dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
+dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
+dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
+...
+-------------------------------------------------
+
+Dangling objects are objects that are harmless, but also unnecessary;
+you can remove them at any time with gitlink:git-prune[1] or the --prune
+option to gitlink:git-gc[1]:
+
+-------------------------------------------------
+$ git gc --prune
+-------------------------------------------------
+
+This may be time-consuming. Unlike most other git operations (including
+git-gc when run without any options), it is not safe to prune while
+other git operations are in progress in the same repository.
+
+For more about dangling objects, see <<dangling-objects>>.
+
+
+Recovering lost changes
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Reflogs
+^^^^^^^
+
+Say you modify a branch with gitlink:git-reset[1] --hard, and then
+realize that the branch was the only reference you had to that point in
+history.
+
+Fortunately, git also keeps a log, called a "reflog", of all the
+previous values of each branch. So in this case you can still find the
+old history using, for example,
+
+-------------------------------------------------
+$ git log master@{1}
+-------------------------------------------------
+
+This lists the commits reachable from the previous version of the head.
+This syntax can be used to with any git command that accepts a commit,
+not just with git log. Some other examples:
+
+-------------------------------------------------
+$ git show master@{2} # See where the branch pointed 2,
+$ git show master@{3} # 3, ... changes ago.
+$ gitk master@{yesterday} # See where it pointed yesterday,
+$ gitk master@{"1 week ago"} # ... or last week
+-------------------------------------------------
+
+The reflogs are kept by default for 30 days, after which they may be
+pruned. See gitlink:git-reflog[1] and gitlink:git-gc[1] to learn
+how to control this pruning, and see the "SPECIFYING REVISIONS"
+section of gitlink:git-rev-parse[1] for details.
+
+Note that the reflog history is very different from normal git history.
+While normal history is shared by every repository that works on the
+same project, the reflog history is not shared: it tells you only about
+how the branches in your local repository have changed over time.
+
+Examining dangling objects
+^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In some situations the reflog may not be able to save you. For
+example, suppose you delete a branch, then realize you need the history
+it pointed you. The reflog is also deleted; however, if you have not
+yet pruned the repository, then you may still be able to find
+the lost commits; run git-fsck and watch for output that mentions
+"dangling commits":
+
+-------------------------------------------------
+$ git fsck
+dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
+dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
+dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
+...
+-------------------------------------------------
+
+and watch for output that mentions "dangling commits". You can examine
+one of those dangling commits with, for example,
+
+------------------------------------------------
+$ gitk 7281251ddd --not --all
+------------------------------------------------
+
+which does what it sounds like: it says that you want to see the commit
+history that is described by the dangling commit(s), but not the
+history that is described by all your existing branches and tags. Thus
+you get exactly the history reachable from that commit that is lost.
+(And notice that it might not be just one commit: we only report the
+"tip of the line" as being dangling, but there might be a whole deep
+and complex commit history that was gotten dropped.)
+
+If you decide you want the history back, you can always create a new
+reference pointing to it, for example, a new branch:
+
+------------------------------------------------
+$ git branch recovered-branch 7281251ddd
+------------------------------------------------
+
+
+Sharing development with others
+===============================
+
+[[getting-updates-with-git-pull]]
+Getting updates with git pull
+-----------------------------
+
+After you clone a repository and make a few changes of your own, you
+may wish to check the original repository for updates and merge them
+into your own work.
+
+We have already seen <<Updating-a-repository-with-git-fetch,how to
+keep remote tracking branches up to date>> with gitlink:git-fetch[1],
+and how to merge two branches. So you can merge in changes from the
+original repository's master branch with:
+
+-------------------------------------------------
+$ git fetch
+$ git merge origin/master
+-------------------------------------------------
+
+However, the gitlink:git-pull[1] command provides a way to do this in
+one step:
+
+-------------------------------------------------
+$ git pull origin master
+-------------------------------------------------
+
+In fact, "origin" is normally the default repository to pull from,
+and the default branch is normally the HEAD of the remote repository,
+so often you can accomplish the above with just
+
+-------------------------------------------------
+$ git pull
+-------------------------------------------------
+
+See the descriptions of the branch.<name>.remote and
+branch.<name>.merge options in gitlink:git-config[1] to learn
+how to control these defaults depending on the current branch.
+
+In addition to saving you keystrokes, "git pull" also helps you by
+producing a default commit message documenting the branch and
+repository that you pulled from.
+
+(But note that no such commit will be created in the case of a
+<<fast-forwards,fast forward>>; instead, your branch will just be
+updated to point to the latest commit from the upstream branch).
+
+The git-pull command can also be given "." as the "remote" repository,
+in which case it just merges in a branch from the current repository; so
+the commands
+
+-------------------------------------------------
+$ git pull . branch
+$ git merge branch
+-------------------------------------------------
+
+are roughly equivalent. The former is actually very commonly used.
+
+Submitting patches to a project
+-------------------------------
+
+If you just have a few changes, the simplest way to submit them may
+just be to send them as patches in email:
+
+First, use gitlink:git-format-patch[1]; for example:
+
+-------------------------------------------------
+$ git format-patch origin
+-------------------------------------------------
+
+will produce a numbered series of files in the current directory, one
+for each patch in the current branch but not in origin/HEAD.
+
+You can then import these into your mail client and send them by
+hand. However, if you have a lot to send at once, you may prefer to
+use the gitlink:git-send-email[1] script to automate the process.
+Consult the mailing list for your project first to determine how they
+prefer such patches be handled.
+
+Importing patches to a project
+------------------------------
+
+Git also provides a tool called gitlink:git-am[1] (am stands for
+"apply mailbox"), for importing such an emailed series of patches.
+Just save all of the patch-containing messages, in order, into a
+single mailbox file, say "patches.mbox", then run
+
+-------------------------------------------------
+$ git am -3 patches.mbox
+-------------------------------------------------
+
+Git will apply each patch in order; if any conflicts are found, it
+will stop, and you can fix the conflicts as described in
+"<<resolving-a-merge,Resolving a merge>>". (The "-3" option tells
+git to perform a merge; if you would prefer it just to abort and
+leave your tree and index untouched, you may omit that option.)
+
+Once the index is updated with the results of the conflict
+resolution, instead of creating a new commit, just run
+
+-------------------------------------------------
+$ git am --resolved
+-------------------------------------------------
+
+and git will create the commit for you and continue applying the
+remaining patches from the mailbox.
+
+The final result will be a series of commits, one for each patch in
+the original mailbox, with authorship and commit log message each
+taken from the message containing each patch.
+
+[[setting-up-a-public-repository]]
+Setting up a public repository
+------------------------------
+
+Another way to submit changes to a project is to simply tell the
+maintainer of that project to pull from your repository, exactly as
+you did in the section "<<getting-updates-with-git-pull, Getting
+updates with git pull>>".
+
+If you and maintainer both have accounts on the same machine, then
+then you can just pull changes from each other's repositories
+directly; note that all of the command (gitlink:git-clone[1],
+git-fetch[1], git-pull[1], etc.) which accept a URL as an argument
+will also accept a local file patch; so, for example, you can
+use
+
+-------------------------------------------------
+$ git clone /path/to/repository
+$ git pull /path/to/other/repository
+-------------------------------------------------
+
+If this sort of setup is inconvenient or impossible, another (more
+common) option is to set up a public repository on a public server.
+This also allows you to cleanly separate private work in progress
+from publicly visible work.
+
+You will continue to do your day-to-day work in your personal
+repository, but periodically "push" changes from your personal
+repository into your public repository, allowing other developers to
+pull from that repository. So the flow of changes, in a situation
+where there is one other developer with a public repository, looks
+like this:
+
+ you push
+ your personal repo ------------------> your public repo
+ ^ |
+ | |
+ | you pull | they pull
+ | |
+ | |
+ | they push V
+ their public repo <------------------- their repo
+
+Now, assume your personal repository is in the directory ~/proj. We
+first create a new clone of the repository:
+
+-------------------------------------------------
+$ git clone --bare proj-clone.git
+-------------------------------------------------
+
+The resulting directory proj-clone.git will contains a "bare" git
+repository--it is just the contents of the ".git" directory, without
+a checked-out copy of a working directory.
+
+Next, copy proj-clone.git to the server where you plan to host the
+public repository. You can use scp, rsync, or whatever is most
+convenient.
+
+If somebody else maintains the public server, they may already have
+set up a git service for you, and you may skip to the section
+"<<pushing-changes-to-a-public-repository,Pushing changes to a public
+repository>>", below.
+
+Otherwise, the following sections explain how to export your newly
+created public repository:
+
+[[exporting-via-http]]
+Exporting a git repository via http
+-----------------------------------
+
+The git protocol gives better performance and reliability, but on a
+host with a web server set up, http exports may be simpler to set up.
+
+All you need to do is place the newly created bare git repository in
+a directory that is exported by the web server, and make some
+adjustments to give web clients some extra information they need:
+
+-------------------------------------------------
+$ mv proj.git /home/you/public_html/proj.git
+$ cd proj.git
+$ git update-server-info
+$ chmod a+x hooks/post-update
+-------------------------------------------------
+
+(For an explanation of the last two lines, see
+gitlink:git-update-server-info[1], and the documentation
+link:hooks.txt[Hooks used by git].)
+
+Advertise the url of proj.git. Anybody else should then be able to
+clone or pull from that url, for example with a commandline like:
+
+-------------------------------------------------
+$ git clone http://yourserver.com/~you/proj.git
+-------------------------------------------------
+
+(See also
+link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
+for a slightly more sophisticated setup using WebDAV which also
+allows pushing over http.)
+
+[[exporting-via-git]]
+Exporting a git repository via the git protocol
+-----------------------------------------------
+
+This is the preferred method.
+
+For now, we refer you to the gitlink:git-daemon[1] man page for
+instructions. (See especially the examples section.)
+
+[[pushing-changes-to-a-public-repository]]
+Pushing changes to a public repository
+--------------------------------------
+
+Note that the two techniques outline above (exporting via
+<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
+maintainers to fetch your latest changes, but they do not allow write
+access, which you will need to update the public repository with the
+latest changes created in your private repository.
+
+The simplest way to do this is using gitlink:git-push[1] and ssh; to
+update the remote branch named "master" with the latest state of your
+branch named "master", run
+
+-------------------------------------------------
+$ git push ssh://yourserver.com/~you/proj.git master:master
+-------------------------------------------------
+
+or just
+
+-------------------------------------------------
+$ git push ssh://yourserver.com/~you/proj.git master
+-------------------------------------------------
+
+As with git-fetch, git-push will complain if this does not result in
+a <<fast-forwards,fast forward>>. Normally this is a sign of
+something wrong. However, if you are sure you know what you're
+doing, you may force git-push to perform the update anyway by
+proceeding the branch name by a plus sign:
+
+-------------------------------------------------
+$ git push ssh://yourserver.com/~you/proj.git +master
+-------------------------------------------------
+
+As with git-fetch, you may also set up configuration options to
+save typing; so, for example, after
+
+-------------------------------------------------
+$ cat >.git/config <<EOF
+[remote "public-repo"]
+ url = ssh://yourserver.com/~you/proj.git
+EOF
+-------------------------------------------------
+
+you should be able to perform the above push with just
+
+-------------------------------------------------
+$ git push public-repo master
+-------------------------------------------------
+
+See the explanations of the remote.<name>.url, branch.<name>.remote,
+and remote.<name>.push options in gitlink:git-config[1] for
+details.
+
+Setting up a shared repository
+------------------------------
+
+Another way to collaborate is by using a model similar to that
+commonly used in CVS, where several developers with special rights
+all push to and pull from a single shared repository. See
+link:cvs-migration.txt[git for CVS users] for instructions on how to
+set this up.
+
+Allow web browsing of a repository
+----------------------------------
+
+The gitweb cgi script provides users an easy way to browse your
+project's files and history without having to install git; see the file
+gitweb/README in the git source tree for instructions on setting it up.
+
+Examples
+--------
+
+TODO: topic branches, typical roles as in everyday.txt, ?
+
+
+[[cleaning-up-history]]
+Rewriting history and maintaining patch series
+==============================================
+
+Normally commits are only added to a project, never taken away or
+replaced. Git is designed with this assumption, and violating it will
+cause git's merge machinery (for example) to do the wrong thing.
+
+However, there is a situation in which it can be useful to violate this
+assumption.
+
+Creating the perfect patch series
+---------------------------------
+
+Suppose you are a contributor to a large project, and you want to add a
+complicated feature, and to present it to the other developers in a way
+that makes it easy for them to read your changes, verify that they are
+correct, and understand why you made each change.
+
+If you present all of your changes as a single patch (or commit), they
+may find it is too much to digest all at once.
+
+If you present them with the entire history of your work, complete with
+mistakes, corrections, and dead ends, they may be overwhelmed.
+
+So the ideal is usually to produce a series of patches such that:
+
+ 1. Each patch can be applied in order.
+
+ 2. Each patch includes a single logical change, together with a
+ message explaining the change.
+
+ 3. No patch introduces a regression: after applying any initial
+ part of the series, the resulting project still compiles and
+ works, and has no bugs that it didn't have before.
+
+ 4. The complete series produces the same end result as your own
+ (probably much messier!) development process did.
+
+We will introduce some tools that can help you do this, explain how to
+use them, and then explain some of the problems that can arise because
+you are rewriting history.
+
+Keeping a patch series up to date using git-rebase
+--------------------------------------------------
+
+Suppose you have a series of commits in a branch "mywork", which
+originally branched off from "origin".
+
+Suppose you create a branch "mywork" on a remote-tracking branch
+"origin", and created some commits on top of it:
+
+-------------------------------------------------
+$ git checkout -b mywork origin
+$ vi file.txt
+$ git commit
+$ vi otherfile.txt
+$ git commit
+...
+-------------------------------------------------
+
+You have performed no merges into mywork, so it is just a simple linear
+sequence of patches on top of "origin":
+
+
+ o--o--o <-- origin
+ \
+ o--o--o <-- mywork
+
+Some more interesting work has been done in the upstream project, and
+"origin" has advanced:
+
+ o--o--O--o--o--o <-- origin
+ \
+ a--b--c <-- mywork
+
+At this point, you could use "pull" to merge your changes back in;
+the result would create a new merge commit, like this:
+
+
+ o--o--O--o--o--o <-- origin
+ \ \
+ a--b--c--m <-- mywork
+
+However, if you prefer to keep the history in mywork a simple series of
+commits without any merges, you may instead choose to use
+gitlink:git-rebase[1]:
+
+-------------------------------------------------
+$ git checkout mywork
+$ git rebase origin
+-------------------------------------------------
+
+This will remove each of your commits from mywork, temporarily saving
+them as patches (in a directory named ".dotest"), update mywork to
+point at the latest version of origin, then apply each of the saved
+patches to the new mywork. The result will look like:
+
+
+ o--o--O--o--o--o <-- origin
+ \
+ a'--b'--c' <-- mywork
+
+In the process, it may discover conflicts. In that case it will stop
+and allow you to fix the conflicts; after fixing conflicts, use "git
+add" to update the index with those contents, and then, instead of
+running git-commit, just run
+
+-------------------------------------------------
+$ git rebase --continue
+-------------------------------------------------
+
+and git will continue applying the rest of the patches.
+
+At any point you may use the --abort option to abort this process and
+return mywork to the state it had before you started the rebase:
+
+-------------------------------------------------
+$ git rebase --abort
+-------------------------------------------------
+
+Reordering or selecting from a patch series
+-------------------------------------------
+
+Given one existing commit, the gitlink:git-cherry-pick[1] command
+allows you to apply the change introduced by that commit and create a
+new commit that records it. So, for example, if "mywork" points to a
+series of patches on top of "origin", you might do something like:
+
+-------------------------------------------------
+$ git checkout -b mywork-new origin
+$ gitk origin..mywork &
+-------------------------------------------------
+
+And browse through the list of patches in the mywork branch using gitk,
+applying them (possibly in a different order) to mywork-new using
+cherry-pick, and possibly modifying them as you go using commit
+--amend.
+
+Another technique is to use git-format-patch to create a series of
+patches, then reset the state to before the patches:
+
+-------------------------------------------------
+$ git format-patch origin
+$ git reset --hard origin
+-------------------------------------------------
+
+Then modify, reorder, or eliminate patches as preferred before applying
+them again with gitlink:git-am[1].
+
+Other tools
+-----------
+
+There are numerous other tools, such as stgit, which exist for the
+purpose of maintaining a patch series. These are out of the scope of
+this manual.
+
+Problems with rewriting history
+-------------------------------
+
+The primary problem with rewriting the history of a branch has to do
+with merging. Suppose somebody fetches your branch and merges it into
+their branch, with a result something like this:
+
+ o--o--O--o--o--o <-- origin
+ \ \
+ t--t--t--m <-- their branch:
+
+Then suppose you modify the last three commits:
+
+ o--o--o <-- new head of origin
+ /
+ o--o--O--o--o--o <-- old head of origin
+
+If we examined all this history together in one repository, it will
+look like:
+
+ o--o--o <-- new head of origin
+ /
+ o--o--O--o--o--o <-- old head of origin
+ \ \
+ t--t--t--m <-- their branch:
+
+Git has no way of knowing that the new head is an updated version of
+the old head; it treats this situation exactly the same as it would if
+two developers had independently done the work on the old and new heads
+in parallel. At this point, if someone attempts to merge the new head
+in to their branch, git will attempt to merge together the two (old and
+new) lines of development, instead of trying to replace the old by the
+new. The results are likely to be unexpected.
+
+You may still choose to publish branches whose history is rewritten,
+and it may be useful for others to be able to fetch those branches in
+order to examine or test them, but they should not attempt to pull such
+branches into their own work.
+
+For true distributed development that supports proper merging,
+published branches should never be rewritten.
+
+Advanced branch management
+==========================
+
+Fetching individual branches
+----------------------------
+
+Instead of using gitlink:git-remote[1], you can also choose just
+to update one branch at a time, and to store it locally under an
+arbitrary name:
+
+-------------------------------------------------
+$ git fetch origin todo:my-todo-work
+-------------------------------------------------
+
+The first argument, "origin", just tells git to fetch from the
+repository you originally cloned from. The second argument tells git
+to fetch the branch named "todo" from the remote repository, and to
+store it locally under the name refs/heads/my-todo-work.
+
+You can also fetch branches from other repositories; so
+
+-------------------------------------------------
+$ git fetch git://example.com/proj.git master:example-master
+-------------------------------------------------
+
+will create a new branch named "example-master" and store in it the
+branch named "master" from the repository at the given URL. If you
+already have a branch named example-master, it will attempt to
+"fast-forward" to the commit given by example.com's master branch. So
+next we explain what a fast-forward is:
+
+[[fast-forwards]]
+Understanding git history: fast-forwards
+----------------------------------------
+
+In the previous example, when updating an existing branch, "git
+fetch" checks to make sure that the most recent commit on the remote
+branch is a descendant of the most recent commit on your copy of the
+branch before updating your copy of the branch to point at the new
+commit. Git calls this process a "fast forward".
+
+A fast forward looks something like this:
+
+ o--o--o--o <-- old head of the branch
+ \
+ o--o--o <-- new head of the branch
+
+
+In some cases it is possible that the new head will *not* actually be
+a descendant of the old head. For example, the developer may have
+realized she made a serious mistake, and decided to backtrack,
+resulting in a situation like:
+
+ o--o--o--o--a--b <-- old head of the branch
+ \
+ o--o--o <-- new head of the branch
+
+
+
+In this case, "git fetch" will fail, and print out a warning.
+
+In that case, you can still force git to update to the new head, as
+described in the following section. However, note that in the
+situation above this may mean losing the commits labeled "a" and "b",
+unless you've already created a reference of your own pointing to
+them.
+
+Forcing git fetch to do non-fast-forward updates
+------------------------------------------------
+
+If git fetch fails because the new head of a branch is not a
+descendant of the old head, you may force the update with:
+
+-------------------------------------------------
+$ git fetch git://example.com/proj.git +master:refs/remotes/example/master
+-------------------------------------------------
+
+Note the addition of the "+" sign. Be aware that commits which the
+old version of example/master pointed at may be lost, as we saw in
+the previous section.
+
+Configuring remote branches
+---------------------------
+
+We saw above that "origin" is just a shortcut to refer to the
+repository which you originally cloned from. This information is
+stored in git configuration variables, which you can see using
+gitlink:git-config[1]:
+
+-------------------------------------------------
+$ git config -l
+core.repositoryformatversion=0
+core.filemode=true
+core.logallrefupdates=true
+remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
+remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
+branch.master.remote=origin
+branch.master.merge=refs/heads/master
+-------------------------------------------------
+
+If there are other repositories that you also use frequently, you can
+create similar configuration options to save typing; for example,
+after
+
+-------------------------------------------------
+$ git config remote.example.url git://example.com/proj.git
+-------------------------------------------------
+
+then the following two commands will do the same thing:
+
+-------------------------------------------------
+$ git fetch git://example.com/proj.git master:refs/remotes/example/master
+$ git fetch example master:refs/remotes/example/master
+-------------------------------------------------
+
+Even better, if you add one more option:
+
+-------------------------------------------------
+$ git config remote.example.fetch master:refs/remotes/example/master
+-------------------------------------------------
+
+then the following commands will all do the same thing:
+
+-------------------------------------------------
+$ git fetch git://example.com/proj.git master:ref/remotes/example/master
+$ git fetch example master:ref/remotes/example/master
+$ git fetch example example/master
+$ git fetch example
+-------------------------------------------------
+
+You can also add a "+" to force the update each time:
+
+-------------------------------------------------
+$ git config remote.example.fetch +master:ref/remotes/example/master
+-------------------------------------------------
+
+Don't do this unless you're sure you won't mind "git fetch" possibly
+throwing away commits on mybranch.
+
+Also note that all of the above configuration can be performed by
+directly editing the file .git/config instead of using
+gitlink:git-config[1].
+
+See gitlink:git-config[1] for more details on the configuration
+options mentioned above.
+
+
+Git internals
+=============
+
+There are two object abstractions: the "object database", and the
+"current directory cache" aka "index".
+
+The Object Database
+-------------------
+
+The object database is literally just a content-addressable collection
+of objects. All objects are named by their content, which is
+approximated by the SHA1 hash of the object itself. Objects may refer
+to other objects (by referencing their SHA1 hash), and so you can
+build up a hierarchy of objects.
+
+All objects have a statically determined "type" aka "tag", which is
+determined at object creation time, and which identifies the format of
+the object (i.e. how it is used, and how it can refer to other
+objects). There are currently four different object types: "blob",
+"tree", "commit" and "tag".
+
+A "blob" object cannot refer to any other object, and is, like the type
+implies, a pure storage object containing some user data. It is used to
+actually store the file data, i.e. a blob object is associated with some
+particular version of some file.
+
+A "tree" object is an object that ties one or more "blob" objects into a
+directory structure. In addition, a tree object can refer to other tree
+objects, thus creating a directory hierarchy.
+
+A "commit" object ties such directory hierarchies together into
+a DAG of revisions - each "commit" is associated with exactly one tree
+(the directory hierarchy at the time of the commit). In addition, a
+"commit" refers to one or more "parent" commit objects that describe the
+history of how we arrived at that directory hierarchy.
+
+As a special case, a commit object with no parents is called the "root"
+object, and is the point of an initial project commit. Each project
+must have at least one root, and while you can tie several different
+root objects together into one project by creating a commit object which
+has two or more separate roots as its ultimate parents, that's probably
+just going to confuse people. So aim for the notion of "one root object
+per project", even if git itself does not enforce that.
+
+A "tag" object symbolically identifies and can be used to sign other
+objects. It contains the identifier and type of another object, a
+symbolic name (of course!) and, optionally, a signature.
+
+Regardless of object type, all objects share the following
+characteristics: they are all deflated with zlib, and have a header
+that not only specifies their type, but also provides size information
+about the data in the object. It's worth noting that the SHA1 hash
+that is used to name the object is the hash of the original data
+plus this header, so `sha1sum` 'file' does not match the object name
+for 'file'.
+(Historical note: in the dawn of the age of git the hash
+was the sha1 of the 'compressed' object.)
+
+As a result, the general consistency of an object can always be tested
+independently of the contents or the type of the object: all objects can
+be validated by verifying that (a) their hashes match the content of the
+file and (b) the object successfully inflates to a stream of bytes that
+forms a sequence of <ascii type without space> + <space> + <ascii decimal
+size> + <byte\0> + <binary object data>.
+
+The structured objects can further have their structure and
+connectivity to other objects verified. This is generally done with
+the `git-fsck` program, which generates a full dependency graph
+of all objects, and verifies their internal consistency (in addition
+to just verifying their superficial consistency through the hash).
+
+The object types in some more detail:
+
+Blob Object
+-----------
+
+A "blob" object is nothing but a binary blob of data, and doesn't
+refer to anything else. There is no signature or any other
+verification of the data, so while the object is consistent (it 'is'
+indexed by its sha1 hash, so the data itself is certainly correct), it
+has absolutely no other attributes. No name associations, no
+permissions. It is purely a blob of data (i.e. normally "file
+contents").
+
+In particular, since the blob is entirely defined by its data, if two
+files in a directory tree (or in multiple different versions of the
+repository) have the same contents, they will share the same blob
+object. The object is totally independent of its location in the
+directory tree, and renaming a file does not change the object that
+file is associated with in any way.
+
+A blob is typically created when gitlink:git-update-index[1]
+is run, and its data can be accessed by gitlink:git-cat-file[1].
+
+Tree Object
+-----------
+
+The next hierarchical object type is the "tree" object. A tree object
+is a list of mode/name/blob data, sorted by name. Alternatively, the
+mode data may specify a directory mode, in which case instead of
+naming a blob, that name is associated with another TREE object.
+
+Like the "blob" object, a tree object is uniquely determined by the
+set contents, and so two separate but identical trees will always
+share the exact same object. This is true at all levels, i.e. it's
+true for a "leaf" tree (which does not refer to any other trees, only
+blobs) as well as for a whole subdirectory.
+
+For that reason a "tree" object is just a pure data abstraction: it
+has no history, no signatures, no verification of validity, except
+that since the contents are again protected by the hash itself, we can
+trust that the tree is immutable and its contents never change.
+
+So you can trust the contents of a tree to be valid, the same way you
+can trust the contents of a blob, but you don't know where those
+contents 'came' from.
+
+Side note on trees: since a "tree" object is a sorted list of
+"filename+content", you can create a diff between two trees without
+actually having to unpack two trees. Just ignore all common parts,
+and your diff will look right. In other words, you can effectively
+(and efficiently) tell the difference between any two random trees by
+O(n) where "n" is the size of the difference, rather than the size of
+the tree.
+
+Side note 2 on trees: since the name of a "blob" depends entirely and
+exclusively on its contents (i.e. there are no names or permissions
+involved), you can see trivial renames or permission changes by
+noticing that the blob stayed the same. However, renames with data
+changes need a smarter "diff" implementation.
+
+A tree is created with gitlink:git-write-tree[1] and
+its data can be accessed by gitlink:git-ls-tree[1].
+Two trees can be compared with gitlink:git-diff-tree[1].
+
+Commit Object
+-------------
+
+The "commit" object is an object that introduces the notion of
+history into the picture. In contrast to the other objects, it
+doesn't just describe the physical state of a tree, it describes how
+we got there, and why.
+
+A "commit" is defined by the tree-object that it results in, the
+parent commits (zero, one or more) that led up to that point, and a
+comment on what happened. Again, a commit is not trusted per se:
+the contents are well-defined and "safe" due to the cryptographically
+strong signatures at all levels, but there is no reason to believe
+that the tree is "good" or that the merge information makes sense.
+The parents do not have to actually have any relationship with the
+result, for example.
+
+Note on commits: unlike real SCM's, commits do not contain
+rename information or file mode change information. All of that is
+implicit in the trees involved (the result tree, and the result trees
+of the parents), and describing that makes no sense in this idiotic
+file manager.
+
+A commit is created with gitlink:git-commit-tree[1] and
+its data can be accessed by gitlink:git-cat-file[1].
+
+Trust
+-----
+
+An aside on the notion of "trust". Trust is really outside the scope
+of "git", but it's worth noting a few things. First off, since
+everything is hashed with SHA1, you 'can' trust that an object is
+intact and has not been messed with by external sources. So the name
+of an object uniquely identifies a known state - just not a state that
+you may want to trust.
+
+Furthermore, since the SHA1 signature of a commit refers to the
+SHA1 signatures of the tree it is associated with and the signatures
+of the parent, a single named commit specifies uniquely a whole set
+of history, with full contents. You can't later fake any step of the
+way once you have the name of a commit.
+
+So to introduce some real trust in the system, the only thing you need
+to do is to digitally sign just 'one' special note, which includes the
+name of a top-level commit. Your digital signature shows others
+that you trust that commit, and the immutability of the history of
+commits tells others that they can trust the whole history.
+
+In other words, you can easily validate a whole archive by just
+sending out a single email that tells the people the name (SHA1 hash)
+of the top commit, and digitally sign that email using something
+like GPG/PGP.
+
+To assist in this, git also provides the tag object...
+
+Tag Object
+----------
+
+Git provides the "tag" object to simplify creating, managing and
+exchanging symbolic and signed tokens. The "tag" object at its
+simplest simply symbolically identifies another object by containing
+the sha1, type and symbolic name.
+
+However it can optionally contain additional signature information
+(which git doesn't care about as long as there's less than 8k of
+it). This can then be verified externally to git.
+
+Note that despite the tag features, "git" itself only handles content
+integrity; the trust framework (and signature provision and
+verification) has to come from outside.
+
+A tag is created with gitlink:git-mktag[1],
+its data can be accessed by gitlink:git-cat-file[1],
+and the signature can be verified by
+gitlink:git-verify-tag[1].
+
+
+The "index" aka "Current Directory Cache"
+-----------------------------------------
+
+The index is a simple binary file, which contains an efficient
+representation of a virtual directory content at some random time. It
+does so by a simple array that associates a set of names, dates,
+permissions and content (aka "blob") objects together. The cache is
+always kept ordered by name, and names are unique (with a few very
+specific rules) at any point in time, but the cache has no long-term
+meaning, and can be partially updated at any time.
+
+In particular, the index certainly does not need to be consistent with
+the current directory contents (in fact, most operations will depend on
+different ways to make the index 'not' be consistent with the directory
+hierarchy), but it has three very important attributes:
+
+'(a) it can re-generate the full state it caches (not just the
+directory structure: it contains pointers to the "blob" objects so
+that it can regenerate the data too)'
+
+As a special case, there is a clear and unambiguous one-way mapping
+from a current directory cache to a "tree object", which can be
+efficiently created from just the current directory cache without
+actually looking at any other data. So a directory cache at any one
+time uniquely specifies one and only one "tree" object (but has
+additional data to make it easy to match up that tree object with what
+has happened in the directory)
+
+'(b) it has efficient methods for finding inconsistencies between that
+cached state ("tree object waiting to be instantiated") and the
+current state.'
+
+'(c) it can additionally efficiently represent information about merge
+conflicts between different tree objects, allowing each pathname to be
+associated with sufficient information about the trees involved that
+you can create a three-way merge between them.'
+
+Those are the three ONLY things that the directory cache does. It's a
+cache, and the normal operation is to re-generate it completely from a
+known tree object, or update/compare it with a live tree that is being
+developed. If you blow the directory cache away entirely, you generally
+haven't lost any information as long as you have the name of the tree
+that it described.
+
+At the same time, the index is at the same time also the
+staging area for creating new trees, and creating a new tree always
+involves a controlled modification of the index file. In particular,
+the index file can have the representation of an intermediate tree that
+has not yet been instantiated. So the index can be thought of as a
+write-back cache, which can contain dirty information that has not yet
+been written back to the backing store.
+
+
+
+The Workflow
+------------
+
+Generally, all "git" operations work on the index file. Some operations
+work *purely* on the index file (showing the current state of the
+index), but most operations move data to and from the index file. Either
+from the database or from the working directory. Thus there are four
+main combinations:
+
+working directory -> index
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You update the index with information from the working directory with
+the gitlink:git-update-index[1] command. You
+generally update the index information by just specifying the filename
+you want to update, like so:
+
+-------------------------------------------------
+$ git-update-index filename
+-------------------------------------------------
+
+but to avoid common mistakes with filename globbing etc, the command
+will not normally add totally new entries or remove old entries,
+i.e. it will normally just update existing cache entries.
+
+To tell git that yes, you really do realize that certain files no
+longer exist, or that new files should be added, you
+should use the `--remove` and `--add` flags respectively.
+
+NOTE! A `--remove` flag does 'not' mean that subsequent filenames will
+necessarily be removed: if the files still exist in your directory
+structure, the index will be updated with their new status, not
+removed. The only thing `--remove` means is that update-cache will be
+considering a removed file to be a valid thing, and if the file really
+does not exist any more, it will update the index accordingly.
+
+As a special case, you can also do `git-update-index --refresh`, which
+will refresh the "stat" information of each index to match the current
+stat information. It will 'not' update the object status itself, and
+it will only update the fields that are used to quickly test whether
+an object still matches its old backing store object.
+
+index -> object database
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+You write your current index file to a "tree" object with the program
+
+-------------------------------------------------
+$ git-write-tree
+-------------------------------------------------
+
+that doesn't come with any options - it will just write out the
+current index into the set of tree objects that describe that state,
+and it will return the name of the resulting top-level tree. You can
+use that tree to re-generate the index at any time by going in the
+other direction:
+
+object database -> index
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+You read a "tree" file from the object database, and use that to
+populate (and overwrite - don't do this if your index contains any
+unsaved state that you might want to restore later!) your current
+index. Normal operation is just
+
+-------------------------------------------------
+$ git-read-tree <sha1 of tree>
+-------------------------------------------------
+
+and your index file will now be equivalent to the tree that you saved
+earlier. However, that is only your 'index' file: your working
+directory contents have not been modified.
+
+index -> working directory
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+You update your working directory from the index by "checking out"
+files. This is not a very common operation, since normally you'd just
+keep your files updated, and rather than write to your working
+directory, you'd tell the index files about the changes in your
+working directory (i.e. `git-update-index`).
+
+However, if you decide to jump to a new version, or check out somebody
+else's version, or just restore a previous tree, you'd populate your
+index file with read-tree, and then you need to check out the result
+with
+
+-------------------------------------------------
+$ git-checkout-index filename
+-------------------------------------------------
+
+or, if you want to check out all of the index, use `-a`.
+
+NOTE! git-checkout-index normally refuses to overwrite old files, so
+if you have an old version of the tree already checked out, you will
+need to use the "-f" flag ('before' the "-a" flag or the filename) to
+'force' the checkout.
+
+
+Finally, there are a few odds and ends which are not purely moving
+from one representation to the other:
+
+Tying it all together
+~~~~~~~~~~~~~~~~~~~~~
+
+To commit a tree you have instantiated with "git-write-tree", you'd
+create a "commit" object that refers to that tree and the history
+behind it - most notably the "parent" commits that preceded it in
+history.
+
+Normally a "commit" has one parent: the previous state of the tree
+before a certain change was made. However, sometimes it can have two
+or more parent commits, in which case we call it a "merge", due to the
+fact that such a commit brings together ("merges") two or more
+previous states represented by other commits.
+
+In other words, while a "tree" represents a particular directory state
+of a working directory, a "commit" represents that state in "time",
+and explains how we got there.
+
+You create a commit object by giving it the tree that describes the
+state at the time of the commit, and a list of parents:
+
+-------------------------------------------------
+$ git-commit-tree <tree> -p <parent> [-p <parent2> ..]
+-------------------------------------------------
+
+and then giving the reason for the commit on stdin (either through
+redirection from a pipe or file, or by just typing it at the tty).
+
+git-commit-tree will return the name of the object that represents
+that commit, and you should save it away for later use. Normally,
+you'd commit a new `HEAD` state, and while git doesn't care where you
+save the note about that state, in practice we tend to just write the
+result to the file pointed at by `.git/HEAD`, so that we can always see
+what the last committed state was.
+
+Here is an ASCII art by Jon Loeliger that illustrates how
+various pieces fit together.
+
+------------
+
+ commit-tree
+ commit obj
+ +----+
+ | |
+ | |
+ V V
+ +-----------+
+ | Object DB |
+ | Backing |
+ | Store |
+ +-----------+
+ ^
+ write-tree | |
+ tree obj | |
+ | | read-tree
+ | | tree obj
+ V
+ +-----------+
+ | Index |
+ | "cache" |
+ +-----------+
+ update-index ^
+ blob obj | |
+ | |
+ checkout-index -u | | checkout-index
+ stat | | blob obj
+ V
+ +-----------+
+ | Working |
+ | Directory |
+ +-----------+
+
+------------
+
+
+Examining the data
+------------------
+
+You can examine the data represented in the object database and the
+index with various helper tools. For every object, you can use
+gitlink:git-cat-file[1] to examine details about the
+object:
+
+-------------------------------------------------
+$ git-cat-file -t <objectname>
+-------------------------------------------------
+
+shows the type of the object, and once you have the type (which is
+usually implicit in where you find the object), you can use
+
+-------------------------------------------------
+$ git-cat-file blob|tree|commit|tag <objectname>
+-------------------------------------------------
+
+to show its contents. NOTE! Trees have binary content, and as a result
+there is a special helper for showing that content, called
+`git-ls-tree`, which turns the binary content into a more easily
+readable form.
+
+It's especially instructive to look at "commit" objects, since those
+tend to be small and fairly self-explanatory. In particular, if you
+follow the convention of having the top commit name in `.git/HEAD`,
+you can do
+
+-------------------------------------------------
+$ git-cat-file commit HEAD
+-------------------------------------------------
+
+to see what the top commit was.
+
+Merging multiple trees
+----------------------
+
+Git helps you do a three-way merge, which you can expand to n-way by
+repeating the merge procedure arbitrary times until you finally
+"commit" the state. The normal situation is that you'd only do one
+three-way merge (two parents), and commit it, but if you like to, you
+can do multiple parents in one go.
+
+To do a three-way merge, you need the two sets of "commit" objects
+that you want to merge, use those to find the closest common parent (a
+third "commit" object), and then use those commit objects to find the
+state of the directory ("tree" object) at these points.
+
+To get the "base" for the merge, you first look up the common parent
+of two commits with
+
+-------------------------------------------------
+$ git-merge-base <commit1> <commit2>
+-------------------------------------------------
+
+which will return you the commit they are both based on. You should
+now look up the "tree" objects of those commits, which you can easily
+do with (for example)
+
+-------------------------------------------------
+$ git-cat-file commit <commitname> | head -1
+-------------------------------------------------
+
+since the tree object information is always the first line in a commit
+object.
+
+Once you know the three trees you are going to merge (the one "original"
+tree, aka the common case, and the two "result" trees, aka the branches
+you want to merge), you do a "merge" read into the index. This will
+complain if it has to throw away your old index contents, so you should
+make sure that you've committed those - in fact you would normally
+always do a merge against your last commit (which should thus match what
+you have in your current index anyway).
+
+To do the merge, do
+
+-------------------------------------------------
+$ git-read-tree -m -u <origtree> <yourtree> <targettree>
+-------------------------------------------------
+
+which will do all trivial merge operations for you directly in the
+index file, and you can just write the result out with
+`git-write-tree`.
+
+
+Merging multiple trees, continued
+---------------------------------
+
+Sadly, many merges aren't trivial. If there are files that have
+been added.moved or removed, or if both branches have modified the
+same file, you will be left with an index tree that contains "merge
+entries" in it. Such an index tree can 'NOT' be written out to a tree
+object, and you will have to resolve any such merge clashes using
+other tools before you can write out the result.
+
+You can examine such index state with `git-ls-files --unmerged`
+command. An example:
+
+------------------------------------------------
+$ git-read-tree -m $orig HEAD $target
+$ git-ls-files --unmerged
+100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
+100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
+100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c
+------------------------------------------------
+
+Each line of the `git-ls-files --unmerged` output begins with
+the blob mode bits, blob SHA1, 'stage number', and the
+filename. The 'stage number' is git's way to say which tree it
+came from: stage 1 corresponds to `$orig` tree, stage 2 `HEAD`
+tree, and stage3 `$target` tree.
+
+Earlier we said that trivial merges are done inside
+`git-read-tree -m`. For example, if the file did not change
+from `$orig` to `HEAD` nor `$target`, or if the file changed
+from `$orig` to `HEAD` and `$orig` to `$target` the same way,
+obviously the final outcome is what is in `HEAD`. What the
+above example shows is that file `hello.c` was changed from
+`$orig` to `HEAD` and `$orig` to `$target` in a different way.
+You could resolve this by running your favorite 3-way merge
+program, e.g. `diff3` or `merge`, on the blob objects from
+these three stages yourself, like this:
+
+------------------------------------------------
+$ git-cat-file blob 263414f... >hello.c~1
+$ git-cat-file blob 06fa6a2... >hello.c~2
+$ git-cat-file blob cc44c73... >hello.c~3
+$ merge hello.c~2 hello.c~1 hello.c~3
+------------------------------------------------
+
+This would leave the merge result in `hello.c~2` file, along
+with conflict markers if there are conflicts. After verifying
+the merge result makes sense, you can tell git what the final
+merge result for this file is by:
+
+-------------------------------------------------
+$ mv -f hello.c~2 hello.c
+$ git-update-index hello.c
+-------------------------------------------------
+
+When a path is in unmerged state, running `git-update-index` for
+that path tells git to mark the path resolved.
+
+The above is the description of a git merge at the lowest level,
+to help you understand what conceptually happens under the hood.
+In practice, nobody, not even git itself, uses three `git-cat-file`
+for this. There is `git-merge-index` program that extracts the
+stages to temporary files and calls a "merge" script on it:
+
+-------------------------------------------------
+$ git-merge-index git-merge-one-file hello.c
+-------------------------------------------------
+
+and that is what higher level `git resolve` is implemented with.
+
+How git stores objects efficiently: pack files
+----------------------------------------------
+
+We've seen how git stores each object in a file named after the
+object's SHA1 hash.
+
+Unfortunately this system becomes inefficient once a project has a
+lot of objects. Try this on an old project:
+
+------------------------------------------------
+$ git count-objects
+6930 objects, 47620 kilobytes
+------------------------------------------------
+
+The first number is the number of objects which are kept in
+individual files. The second is the amount of space taken up by
+those "loose" objects.
+
+You can save space and make git faster by moving these loose objects in
+to a "pack file", which stores a group of objects in an efficient
+compressed format; the details of how pack files are formatted can be
+found in link:technical/pack-format.txt[technical/pack-format.txt].
+
+To put the loose objects into a pack, just run git repack:
+
+------------------------------------------------
+$ git repack
+Generating pack...
+Done counting 6020 objects.
+Deltifying 6020 objects.
+ 100% (6020/6020) done
+Writing 6020 objects.
+ 100% (6020/6020) done
+Total 6020, written 6020 (delta 4070), reused 0 (delta 0)
+Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.
+------------------------------------------------
+
+You can then run
+
+------------------------------------------------
+$ git prune
+------------------------------------------------
+
+to remove any of the "loose" objects that are now contained in the
+pack. This will also remove any unreferenced objects (which may be
+created when, for example, you use "git reset" to remove a commit).
+You can verify that the loose objects are gone by looking at the
+.git/objects directory or by running
+
+------------------------------------------------
+$ git count-objects
+0 objects, 0 kilobytes
+------------------------------------------------
+
+Although the object files are gone, any commands that refer to those
+objects will work exactly as they did before.
+
+The gitlink:git-gc[1] command performs packing, pruning, and more for
+you, so is normally the only high-level command you need.
+
+[[dangling-objects]]
+Dangling objects
+----------------
+
+The gitlink:git-fsck[1] command will sometimes complain about dangling
+objects. They are not a problem.
+
+The most common cause of dangling objects is that you've rebased a
+branch, or you have pulled from somebody else who rebased a branch--see
+<<cleaning-up-history>>. In that case, the old head of the original
+branch still exists, as does obviously everything it pointed to. The
+branch pointer itself just doesn't, since you replaced it with another
+one.
+
+There are also other situations too that cause dangling objects. For
+example, a "dangling blob" may arise because you did a "git add" of a
+file, but then, before you actually committed it and made it part of the
+bigger picture, you changed something else in that file and committed
+that *updated* thing - the old state that you added originally ends up
+not being pointed to by any commit or tree, so it's now a dangling blob
+object.
+
+Similarly, when the "recursive" merge strategy runs, and finds that
+there are criss-cross merges and thus more than one merge base (which is
+fairly unusual, but it does happen), it will generate one temporary
+midway tree (or possibly even more, if you had lots of criss-crossing
+merges and more than two merge bases) as a temporary internal merge
+base, and again, those are real objects, but the end result will not end
+up pointing to them, so they end up "dangling" in your repository.
+
+Generally, dangling objects aren't anything to worry about. They can
+even be very useful: if you screw something up, the dangling objects can
+be how you recover your old tree (say, you did a rebase, and realized
+that you really didn't want to - you can look at what dangling objects
+you have, and decide to reset your head to some old dangling state).
+
+For commits, the most useful thing to do with dangling objects tends to
+be to do a simple
+
+------------------------------------------------
+$ gitk <dangling-commit-sha-goes-here> --not --all
+------------------------------------------------
+
+For blobs and trees, you can't do the same, but you can examine them.
+You can just do
+
+------------------------------------------------
+$ git show <dangling-blob/tree-sha-goes-here>
+------------------------------------------------
+
+to show what the contents of the blob were (or, for a tree, basically
+what the "ls" for that directory was), and that may give you some idea
+of what the operation was that left that dangling object.
+
+Usually, dangling blobs and trees aren't very interesting. They're
+almost always the result of either being a half-way mergebase (the blob
+will often even have the conflict markers from a merge in it, if you
+have had conflicting merges that you fixed up by hand), or simply
+because you interrupted a "git fetch" with ^C or something like that,
+leaving _some_ of the new objects in the object database, but just
+dangling and useless.
+
+Anyway, once you are sure that you're not interested in any dangling
+state, you can just prune all unreachable objects:
+
+------------------------------------------------
+$ git prune
+------------------------------------------------
+
+and they'll be gone. But you should only run "git prune" on a quiescent
+repository - it's kind of like doing a filesystem fsck recovery: you
+don't want to do that while the filesystem is mounted.
+
+(The same is true of "git-fsck" itself, btw - but since
+git-fsck never actually *changes* the repository, it just reports
+on what it found, git-fsck itself is never "dangerous" to run.
+Running it while somebody is actually changing the repository can cause
+confusing and scary messages, but it won't actually do anything bad. In
+contrast, running "git prune" while somebody is actively changing the
+repository is a *BAD* idea).
+
+Glossary of git terms
+=====================
+
+include::glossary.txt[]
+
+Notes and todo list for this manual
+===================================
+
+This is a work in progress.
+
+The basic requirements:
+ - It must be readable in order, from beginning to end, by
+ someone intelligent with a basic grasp of the unix
+ commandline, but without any special knowledge of git. If
+ necessary, any other prerequisites should be specifically
+ mentioned as they arise.
+ - Whenever possible, section headings should clearly describe
+ the task they explain how to do, in language that requires
+ no more knowledge than necessary: for example, "importing
+ patches into a project" rather than "the git-am command"
+
+Think about how to create a clear chapter dependency graph that will
+allow people to get to important topics without necessarily reading
+everything in between.
+
+Scan Documentation/ for other stuff left out; in particular:
+ howto's
+ some of technical/?
+ hooks
+ list of commands in gitlink:git[1]
+
+Scan email archives for other stuff left out
+
+Scan man pages to see if any assume more background than this manual
+provides.
+
+Simplify beginning by suggesting disconnected head instead of
+temporary branch creation?
+
+Explain how to refer to file stages in the "how to resolve a merge"
+section: diff -1, -2, -3, --ours, --theirs :1:/path notation. The
+"git ls-files --unmerged --stage" thing is sorta useful too,
+actually. And note gitk --merge.
+
+Add more good examples. Entire sections of just cookbook examples
+might be a good idea; maybe make an "advanced examples" section a
+standard end-of-chapter section?
+
+Include cross-references to the glossary, where appropriate.
+
+Document shallow clones? See draft 1.5.0 release notes for some
+documentation.
+
+Add a sectin on working with other version control systems, including
+CVS, Subversion, and just imports of series of release tarballs.
+
+More details on gitweb?
+
+Write a chapter on using plumbing and writing scripts.
projects / git.git / commitdiff