Git User's Manual (for version 1.5.1 or newer)

Chapter 1, Repositories and Branches and Chapter 2, Exploring git history explain how -to fetch and study a project using git—read these chapters to learn how +Git User's Manual (for version 1.5.1 or newer)

Git User's Manual (for version 1.5.1 or newer)

Table of Contents

Preface

1. Repositories and Branches

How to get a git repository

How to check out a different version of a project

Understanding History: Commits

Understanding history: commits, parents, and reachability
Understanding history: History diagrams
Understanding history: What is a branch?

Manipulating branches

Examining an old version without creating a new branch

Examining branches from a remote repository

Naming branches, tags, and other references

Updating a repository with git fetch

Fetching branches from other repositories

2. Exploring git history

How to use bisect to find a regression

Naming commits

Creating tags

Browsing revisions

Generating diffs

Viewing old file versions

Examples

Counting the number of commits on a branch
Check whether two branches point at the same history
Find first tagged version including a given fix
Showing commits unique to a given branch
Creating a changelog and tarball for a software release

Finding commits referencing a file with given content

3. Developing with git

Telling git your name

Creating a new repository

How to make a commit

Creating good commit messages

Ignoring files

How to merge

Resolving a merge

Getting conflict-resolution help during a merge

Undoing a merge

Fast-forward merges

Fixing mistakes

Fixing a mistake with a new commit
Fixing a mistake by editing history
Checking out an old version of a file

Ensuring good performance

Ensuring reliability

Checking the repository for corruption
Recovering lost changes

4. Sharing development with others

Getting updates with git pull

Submitting patches to a project

Importing patches to a project

Public git repositories

Setting up a public repository
Exporting a git repository via the git protocol
Exporting a git repository via http
Pushing changes to a public repository
Setting up a shared repository
Allowing web browsing of a repository

Examples

Maintaining topic branches for a Linux subsystem maintainer

5. Rewriting history and maintaining patch series

Creating the perfect patch series
Keeping a patch series up to date using git-rebase
Modifying a single commit
Reordering or selecting from a patch series
Other tools
Problems with rewriting history

6. Advanced branch management

Fetching individual branches
git fetch and fast-forwards
Forcing git fetch to do non-fast-forward updates
Configuring remote branches

7. Git internals

The Object Database

The "index" aka "Current Directory Cache"

The Workflow

working directory -> index
index -> object database
object database -> index
index -> working directory
Tying it all together

Examining the data

Merging multiple trees

Merging multiple trees, continued

How git stores objects efficiently: pack files

Dangling objects

A birds-eye view of Git's source code

8. GIT Glossary

A. Git Quick Reference

Creating a new repository
Managing branches
Exploring history
Making changes
Merging
Sharing your changes
Repository maintenance

B. Notes and todo list for this manual

Preface

Git is a fast distributed revision control system.

This manual is designed to be readable by someone with basic unix +command-line skills, but no previous knowledge of git.

ChapterÂ 1, Repositories and Branches and ChapterÂ 2, Exploring git history explain how +to fetch and study a project using gitâread these chapters to learn how to build and test a particular version of a software project, search for regressions, and so on.

People needing to do actual development will also want to read -Chapter 3, Developing with git and Chapter 4, Sharing 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

See also Appendix A, Git Quick Reference for a brief overview of git commands, -without any explanation.

Finally, see Appendix B, Notes and todo list for this manual for ways that you can help make this manual more -complete.

Chapter 1. Repositories and Branches

Table of Contents

How to get a git repository

How to check out a different version of a project

Understanding History: Commits

Understanding history: commits, parents, and reachability
Understanding history: History diagrams
Understanding history: What is a branch?

Manipulating branches

Examining an old version without creating a new branch

Examining branches from a remote repository

Naming branches, tags, and other references

Updating a repository with git fetch

Fetching branches from other repositories

How to get a git repository

It will be useful to have a git repository to experiment with as you +ChapterÂ 3, Developing with git and ChapterÂ 4, Sharing 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

$Â manÂ git-clone

See also AppendixÂ A, Git Quick Reference for a brief overview of git commands, +without any explanation.

Finally, see AppendixÂ B, Notes and todo list for this manual for ways that you can help make this manual more +complete.

ChapterÂ 1.Â Repositories and Branches

Table of Contents

How to get a git repository

How to check out a different version of a project

Understanding History: Commits

Understanding history: commits, parents, and reachability
Understanding history: History diagrams
Understanding history: What is a branch?

Manipulating branches

Examining an old version without creating a new branch

Examining branches from a remote repository

Naming branches, tags, and other references

Updating a repository with git fetch

Fetching branches from other repositories

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 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 +are some interesting examples:

Â Â Â Â Â Â Â Â #Â gitÂ itselfÂ (approx.Â 10MBÂ download):
+$Â gitÂ cloneÂ git://git.kernel.org/pub/scm/git/git.git
+Â Â Â Â Â Â Â Â #Â theÂ linuxÂ kernelÂ (approx.Â 150MBÂ download):
+$Â gitÂ cloneÂ 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, @@ -25,12 +25,12 @@ collection of interrelated snapshots (versions) of the project's contents.

A single git repository may contain multiple branches. It keeps track of them by keeping a list of heads which reference the latest version on each branch; the git-branch(1) command shows -you the list of branch heads:

$ git branch
-* master

A freshly cloned repository contains a single branch head, by default +you the list of branch heads:

$Â gitÂ branch
+*Â master

A freshly cloned repository contains a single branch head, by default named "master", with the working directory initialized to the state of the project referred to by that branch head.

Most projects also use tags. Tags, like heads, are references into the project's history, and can be listed using the -git-tag(1) command:

$ git tag -l
+git-tag(1) command:

$Â gitÂ tagÂ -l
v2.6.11
v2.6.11-tree
v2.6.12
@@ -42,42 +42,42 @@ v2.6.12-rc6
v2.6.13
...

Tags are expected to always point at the same version of a project, while heads are expected to advance as development progresses.

Create a new branch head pointing to one of these versions and check it -out using git-checkout(1):

$ git checkout -b new v2.6.13

The working directory then reflects the contents that the project had +out using git-checkout(1):

$Â gitÂ checkoutÂ -bÂ newÂ v2.6.13

The working directory then reflects the contents that the project had when it was tagged v2.6.13, and 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 head was your only reference to a +branches, with an asterisk marking the currently checked-out branch:

$Â gitÂ branch
+Â Â master
+*Â 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

$Â gitÂ resetÂ --hardÂ v2.6.17

Note that if the current branch head 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 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
+current branch:

$Â gitÂ show
+commitÂ 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2
+Author:Â JamalÂ HadiÂ SalimÂ <hadi@cyberus.ca>
+Date:Â Â Â SatÂ DecÂ 2Â 22:22:25Â 2006Â -0800

-    [XFRM]: Fix aevent structuring to be more complete.
+Â Â Â Â [XFRM]:Â FixÂ aeventÂ structuringÂ toÂ beÂ moreÂ 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).
+Â Â Â Â aeventsÂ canÂ notÂ uniquelyÂ identifyÂ anÂ SA.Â WeÂ breakÂ theÂ ABIÂ withÂ this
+Â Â Â Â patch,Â butÂ consensusÂ isÂ thatÂ sinceÂ itÂ isÂ notÂ yetÂ utilizedÂ byÂ any
+Â Â Â Â (known)Â applicationÂ thenÂ itÂ isÂ fineÂ (betterÂ doÂ itÂ nowÂ thanÂ later).

-    Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
-    Signed-off-by: David S. Miller <davem@davemloft.net>
+Â Â Â Â Signed-off-by:Â JamalÂ HadiÂ SalimÂ <hadi@cyberus.ca>
+Â Â Â Â Signed-off-by:Â DavidÂ S.Â MillerÂ <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:
+diffÂ --gitÂ a/Documentation/networking/xfrm_sync.txtÂ b/Documentation/networking/xfrm_sync.txt
+indexÂ 8be626f..d7aac9dÂ 100644
+---Â a/Documentation/networking/xfrm_sync.txt
++++Â b/Documentation/networking/xfrm_sync.txt
+@@Â -47,10Â +47,13Â @@Â aevent_idÂ structureÂ looksÂ like:

-    struct xfrm_aevent_id {
-              struct xfrm_usersa_id           sa_id;
-+             xfrm_address_t                  saddr;
-              __u32                           flags;
-+             __u32                           reqid;
-    };
+Â Â Â Â structÂ xfrm_aevent_idÂ {
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â structÂ xfrm_usersa_idÂ Â Â Â Â Â Â Â Â Â Â sa_id;
++Â Â Â Â Â Â Â Â Â Â Â Â Â xfrm_address_tÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â saddr;
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â __u32Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â flags;
++Â Â Â Â Â Â Â Â Â Â Â Â Â __u32Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â reqid;
+Â Â Â Â };
...

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 @@ -88,7 +88,7 @@ example in email), then you are guaranteed that name will refer to the same commit in their repository that it does in yours (assuming their repository has that commit at all). Since the object name is computed as a hash over the contents of the commit, you are guaranteed that the commit can never change -without its name also changing.

In fact, in Chapter 7, Git internals we shall see that everything stored in git +without its name also changing.

In fact, in ChapterÂ 7, Git internals we shall see that everything stored in git history, including file data and directory contents, is stored in an object with a name that is a hash of its contents.

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. @@ -158,35 +158,35 @@ git checkout -b <new> <start-point> check it out.

The special symbol "HEAD" can always be used to refer to the current branch. In fact, git uses a file named "HEAD" in the .git directory to -remember which branch is current:

$ cat .git/HEAD
-ref: refs/heads/master

Examining an old version without creating a new branch

The git-checkout command normally expects a branch head, but will also +remember which branch is current:

$Â catÂ .git/HEAD
+ref:Â refs/heads/master

Examining an old version without creating a new branch

The git-checkout command normally expects a branch head, but will also accept an arbitrary commit; for example, you can check out the commit -referenced by a tag:

$ git checkout v2.6.17
-Note: moving to "v2.6.17" which isn't a local branch
-If you want to create a new branch from this checkout, you may do so
-(now or later) by using -b with the checkout command again. Example:
- git checkout -b <new_branch_name>
-HEAD is now at 427abfa... Linux v2.6.17

The HEAD then refers to the SHA1 of the commit instead of to a branch, -and git branch shows that you are no longer on a branch:

$ cat .git/HEAD
+referenced by a tag:

$Â gitÂ checkoutÂ v2.6.17
+Note:Â movingÂ toÂ "v2.6.17"Â whichÂ isn'tÂ aÂ localÂ branch
+IfÂ youÂ wantÂ toÂ createÂ aÂ newÂ branchÂ fromÂ thisÂ checkout,Â youÂ mayÂ doÂ so
+(nowÂ orÂ later)Â byÂ usingÂ -bÂ withÂ theÂ checkoutÂ commandÂ again.Â Example:
+Â Â gitÂ checkoutÂ -bÂ <new_branch_name>
+HEADÂ isÂ nowÂ atÂ 427abfa...Â LinuxÂ v2.6.17

The HEAD then refers to the SHA1 of the commit instead of to a branch, +and git branch shows that you are no longer on a branch:

$Â catÂ .git/HEAD
427abfa28afedffadfca9dd8b067eb6d36bac53f
-$ git branch
-* (no branch)
- master

In this case we say that the HEAD is "detached".

This is an easy way to check out a particular version without having to +$Â gitÂ branch
+*Â (noÂ branch)
+Â Â master

In this case we say that the HEAD is "detached".

This is an easy way to check out a particular version without having to make up a name for the new branch. You can still create a new branch (or tag) for this version later if you decide to.

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 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 +can view using the "-r" option to git-branch(1):

$Â gitÂ branchÂ -r
+Â Â origin/HEAD
+Â Â origin/html
+Â Â origin/maint
+Â Â origin/man
+Â Â origin/master
+Â Â origin/next
+Â Â origin/pu
+Â Â 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:

$Â gitÂ checkoutÂ -bÂ my-todo-copyÂ 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.

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 @@ -206,57 +206,57 @@ REVISIONS" section of git-rev-parse(1 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 +repository. It will not touch any of your own branchesânot 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 git-remote(1):

$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git
-$ git fetch linux-nfs
-* 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
+cloned from, using git-remote(1):

$Â gitÂ remoteÂ addÂ linux-nfsÂ git://linux-nfs.org/pub/nfs-2.6.git
+$Â gitÂ fetchÂ linux-nfs
+*Â refs/remotes/linux-nfs/master:Â storingÂ branchÂ 'master'Â ...
+Â Â commit:Â bf81b46

New remote-tracking branches will be stored under the shorthand name +that you gave "git remote add", in this case linux-nfs:

$Â gitÂ branchÂ -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
+a new stanza:

$Â catÂ .git/config
...
-[remote "linux-nfs"]
- url = git://linux-nfs.org/pub/nfs-2.6.git
- fetch = +refs/heads/*:refs/remotes/linux-nfs/*
+[remoteÂ "linux-nfs"]
+Â Â Â Â Â Â Â Â urlÂ =Â git://linux-nfs.org/pub/nfs-2.6.git
+Â Â Â Â Â Â Â Â fetchÂ =Â +refs/heads/*:refs/remotes/linux-nfs/*
...

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 -git-config(1) for details.)

Chapter 2. Exploring git history

Table of Contents

How to use bisect to find a regression

Naming commits

Creating tags

Browsing revisions

Generating diffs

Viewing old file versions

Examples

Counting the number of commits on a branch
Check whether two branches point at the same history
Find first tagged version including a given fix
Showing commits unique to a given branch
Creating a changelog and tarball for a software release

Finding commits referencing a file with given content

Git is best thought of as a tool for storing the history of a +git-config(1) for details.)

ChapterÂ 2.Â Exploring git history

Table of Contents

How to use bisect to find a regression

Naming commits

Creating tags

Browsing revisions

Generating diffs

Viewing old file versions

Examples

Counting the number of commits on a branch
Check whether two branches point at the same history
Find first tagged version including a given fix
Showing commits unique to a given branch
Creating a changelog and tarball for a software release

Finding commits referencing a file with given content

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 contents of a file hierarchy, 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 that 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 -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 +git-bisect(1) command can help you do this:

$Â gitÂ bisectÂ start
+$Â gitÂ bisectÂ goodÂ v2.6.18
+$Â gitÂ bisectÂ badÂ master
+Bisecting:Â 3537Â revisionsÂ leftÂ toÂ testÂ afterÂ this
+[65934a9a028b88e83e2b0f8b36618fe503349f8e]Â BLOCK:Â MakeÂ USBÂ storageÂ dependÂ onÂ SCSIÂ ratherÂ thanÂ selectingÂ itÂ [tryÂ #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 +points to a commit (with commit id 65934â¦) 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 +it crashes. Assume it does crash. Then:

$Â gitÂ bisectÂ bad
+Bisecting:Â 1769Â revisionsÂ leftÂ toÂ testÂ afterÂ this
+[7eff82c8b1511017ae605f0c99ac275a7e21b867]Â i2c-core:Â DropÂ uselessÂ 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 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 +report with the commit id. Finally, run

$Â gitÂ bisectÂ 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 +run

$Â gitÂ bisectÂ 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 +id, and check it out with:

$Â gitÂ resetÂ --hardÂ 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
@@ -270,138 +270,138 @@ tag name: refers to the commit pointed to by the given tag HEAD: refers to the head of the current branch

There are many more; see the "SPECIFYING REVISIONS" section of the 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, +name revisions. Some examples:

$Â gitÂ showÂ fb47ddb2Â #Â theÂ firstÂ fewÂ charactersÂ ofÂ theÂ objectÂ name
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â areÂ usuallyÂ enoughÂ toÂ specifyÂ itÂ uniquely
+$Â gitÂ showÂ HEAD^Â Â Â Â #Â theÂ parentÂ ofÂ theÂ HEADÂ commit
+$Â gitÂ showÂ HEAD^^Â Â Â #Â theÂ grandparent
+$Â gitÂ showÂ HEAD~4Â Â Â #Â theÂ 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 +also choose:

$Â gitÂ showÂ HEAD^1Â Â Â #Â showÂ theÂ firstÂ parentÂ ofÂ HEAD
+$Â gitÂ showÂ HEAD^2Â Â Â #Â showÂ theÂ secondÂ parentÂ ofÂ 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, +specifying a local branch as the target of the operation

$Â gitÂ fetchÂ git://example.com/proj.gitÂ 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 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
+name for that commit:

$Â gitÂ rev-parseÂ 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 you would also like to include a +running

$Â gitÂ tagÂ stable-1Â 1b2e1d63ff

You can use stable-1 to refer to the commit 1b2e1d63ff.

This creates a "lightweight" tag. If you would also like to include a comment with the tag, and possibly sign it cryptographically, then you should create a tag object instead; see the git-tag(1) man page for details.

Browsing revisions

The 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 git-log(1) man page for more +can also make more specific requests:

$Â gitÂ logÂ v2.5..Â Â Â Â Â Â Â Â #Â commitsÂ sinceÂ (notÂ reachableÂ from)Â v2.5
+$Â gitÂ logÂ test..masterÂ Â #Â commitsÂ reachableÂ fromÂ masterÂ butÂ notÂ test
+$Â gitÂ logÂ master..testÂ Â #Â ...reachableÂ fromÂ testÂ butÂ notÂ master
+$Â gitÂ logÂ master...testÂ #Â ...reachableÂ fromÂ eitherÂ testÂ orÂ master,
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â Â Â Â butÂ notÂ both
+$Â gitÂ logÂ --since="2Â weeksÂ ago"Â #Â commitsÂ fromÂ theÂ lastÂ 2Â weeks
+$Â gitÂ logÂ MakefileÂ Â Â Â Â Â #Â commitsÂ whichÂ modifyÂ Makefile
+$Â gitÂ logÂ fs/Â Â Â Â Â Â Â Â Â Â Â #Â ...Â whichÂ modifyÂ anyÂ fileÂ underÂ fs/
+$Â gitÂ logÂ -S'foo()'Â Â Â Â Â #Â commitsÂ whichÂ addÂ orÂ removeÂ anyÂ fileÂ data
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â matchingÂ theÂ stringÂ '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:

$Â gitÂ logÂ v2.5..Â MakefileÂ fs/

You can also ask git log to show patches:

$Â gitÂ logÂ -p

See the "âpretty" option in the 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 independent 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 -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 +git-diff(1):

$Â gitÂ diffÂ master..test

Sometimes what you want instead is a set of patches:

$Â gitÂ format-patchÂ 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 +anything out; this command does that:

$Â gitÂ showÂ 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

Counting the number of commits on a branch

Suppose you want to know how many commits you've made on "mybranch" -since it diverged from "origin":

$ git log --pretty=oneline origin..mybranch | wc -l

Alternatively, you may often see this sort of thing done with the +since it diverged from "origin":

$Â gitÂ logÂ --pretty=onelineÂ origin..mybranchÂ |Â wcÂ -l

Alternatively, you may often see this sort of thing done with the lower-level command git-rev-list(1), which just lists the SHA1's -of all the given commits:

$ git rev-list origin..mybranch | wc -l

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 +of all the given commits:

$Â gitÂ rev-listÂ origin..mybranchÂ |Â wcÂ -l

Check whether two branches point at the same history

Suppose you want to check whether two branches point at the same point +in history.

$Â gitÂ diffÂ 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
+routes. You could compare the object names:

$Â gitÂ rev-listÂ origin
e05db0fd4f31dde7005f075a84f96b360d05984b
-$ git rev-list master
-e05db0fd4f31dde7005f075a84f96b360d05984b

Or you could recall that the … operator selects all commits +$Â gitÂ rev-listÂ master
+e05db0fd4f31dde7005f075a84f96b360d05984b

Or you could recall that the â¦ 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. +both: so

$Â gitÂ logÂ 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 +fix.

Of course, there may be more than one answerâif 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 git-name-rev(1), which will give the commit a +releases.

You could just visually inspect the commits since e05db0fd:

$Â gitkÂ e05db0fd..

Or you can use 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 --tags e05db0fd
-e05db0fd tags/v1.5.0-rc1^0~23

The git-describe(1) command does the opposite, naming the -revision using a tag on which the given commit is based:

$ git describe e05db0fd
+descendants:

$Â gitÂ name-revÂ --tagsÂ e05db0fd
+e05db0fdÂ tags/v1.5.0-rc1^0~23

The git-describe(1) command does the opposite, naming the +revision using a tag on which the given commit is based:

$Â gitÂ describeÂ e05db0fd
v1.5.0-rc0-260-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 git-merge-base(1):

$ git merge-base e05db0fd v1.5.0-rc1
+given commit, you could use git-merge-base(1):

$Â gitÂ merge-baseÂ e05db0fdÂ 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, +actually is an ancestor of v1.5.0-rc1.

Alternatively, note that

$Â gitÂ logÂ 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 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
+you can run something like

$Â gitÂ show-branchÂ e05db0fdÂ v1.5.0-rc0Â v1.5.0-rc1Â v1.5.0-rc2
+!Â [e05db0fd]Â FixÂ warningsÂ inÂ sha1_file.cÂ -Â useÂ C99Â printfÂ formatÂ 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
+Â !Â [v1.5.0-rc0]Â GITÂ v1.5.0Â preview
+Â Â !Â [v1.5.0-rc1]Â GITÂ v1.5.0-rc1
+Â Â Â !Â [v1.5.0-rc2]Â GITÂ v1.5.0-rc2
+...

then search for a line that looks like

+Â ++Â [e05db0fd]Â FixÂ warningsÂ inÂ sha1_file.cÂ -Â useÂ C99Â printfÂ formatÂ 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.

Showing commits unique to a given branch

Suppose you would like to see all the commits reachable from the branch head named "master" but not from any other head in your repository.

We can list all the heads in this repository with -git-show-ref(1):

$ git show-ref --heads
-bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
-db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
-a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
-24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
-1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes

We can get just the branch-head names, and remove "master", with -the help of the standard utilities cut and grep:

$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
+git-show-ref(1):

$Â gitÂ show-refÂ --heads
+bf62196b5e363d73353a9dcf094c59595f3153b7Â refs/heads/core-tutorial
+db768d5504c1bb46f63ee9d6e1772bd047e05bf9Â refs/heads/maint
+a07157ac624b2524a059a3414e99f6f44bebc1e7Â refs/heads/master
+24dbc180ea14dc1aebe09f14c8ecf32010690627Â refs/heads/tutorial-2
+1e87486ae06626c2f31eaa63d26fc0fd646c8af2Â refs/heads/tutorial-fixes

We can get just the branch-head names, and remove "master", with +the help of the standard utilities cut and grep:

$Â gitÂ show-refÂ --headsÂ |Â cutÂ -d'Â 'Â -f2Â |Â grepÂ -vÂ '^refs/heads/master'
refs/heads/core-tutorial
refs/heads/maint
refs/heads/tutorial-2
refs/heads/tutorial-fixes

And then we can ask to see all the commits reachable from master -but not from these other heads:

$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
- grep -v '^refs/heads/master' )

Obviously, endless variations are possible; for example, to see all -commits reachable from some head but not from any tag in the repository:

$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )

(See git-rev-parse(1) for explanations of commit-selecting -syntax such as —not.)

Creating a changelog and tarball for a software release

The git-archive(1) command can create a tar or zip archive from -any version of a project; for example:

$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz

will use HEAD to produce a tar archive in which each filename is +but not from these other heads:

$Â gitkÂ masterÂ --notÂ $(Â gitÂ show-refÂ --headsÂ |Â cutÂ -d'Â 'Â -f2Â |
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â grepÂ -vÂ '^refs/heads/master'Â )

Obviously, endless variations are possible; for example, to see all +commits reachable from some head but not from any tag in the repository:

$Â gitkÂ $(Â gitÂ show-refÂ --headsÂ )Â --notÂ Â $(Â gitÂ show-refÂ --tagsÂ )

(See git-rev-parse(1) for explanations of commit-selecting +syntax such as ânot.)

Creating a changelog and tarball for a software release

The git-archive(1) command can create a tar or zip archive from +any version of a project; for example:

$Â gitÂ archiveÂ --format=tarÂ --prefix=project/Â HEADÂ |Â gzipÂ >latest.tar.gz

will use HEAD to produce a tar archive in which each filename is preceded by "project/".

If you're releasing a new version of a software project, you may want to simultaneously make a changelog to include in the release announcement.

Linus Torvalds, for example, makes new kernel releases by tagging them, -then running:

$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7

where release-script is a shell script that looks like:

#!/bin/sh
+then running:

$Â release-scriptÂ 2.6.12Â 2.6.13-rc6Â 2.6.13-rc7

where release-script is a shell script that looks like:

#!/bin/sh
stable="$1"
last="$2"
new="$3"
-echo "# git tag v$new"
-echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz"
-echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz"
-echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new"
-echo "git shortlog --no-merges v$new ^v$last > ../ShortLog"
-echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"

and then he just cut-and-pastes the output commands after verifying that +echoÂ "#Â gitÂ tagÂ v$new"
+echoÂ "gitÂ archiveÂ --prefix=linux-$new/Â v$newÂ |Â gzipÂ -9Â >Â ../linux-$new.tar.gz"
+echoÂ "gitÂ diffÂ v$stableÂ v$newÂ |Â gzipÂ -9Â >Â ../patch-$new.gz"
+echoÂ "gitÂ logÂ --no-mergesÂ v$newÂ ^v$lastÂ >Â ../ChangeLog-$new"
+echoÂ "gitÂ shortlogÂ --no-mergesÂ v$newÂ ^v$lastÂ >Â ../ShortLog"
+echoÂ "gitÂ diffÂ --statÂ --summaryÂ -MÂ v$lastÂ v$newÂ >Â ../diffstat-$new"

and then he just cut-and-pastes the output commands after verifying that they look OK.

Finding commits referencing a file with given content

Somebody hands you a copy of a file, and asks which commits modified a file such that it contained the given content either before or after the -commit. You can find out with this:

$ git log --raw -r --abbrev=40 --pretty=oneline -- filename |
- grep -B 1 `git hash-object filename`

Figuring out why this works is left as an exercise to the (advanced) +commit. You can find out with this:

$Â Â gitÂ logÂ --rawÂ -rÂ --abbrev=40Â --pretty=onelineÂ --Â filenameÂ |
+Â Â Â Â Â Â Â Â grepÂ -BÂ 1Â `gitÂ hash-objectÂ filename`

Figuring out why this works is left as an exercise to the (advanced) student. The git-log(1), git-diff-tree(1), and -git-hash-object(1) man pages may prove helpful.

Chapter 3. Developing with git

Table of Contents

Telling git your name

Creating a new repository

How to make a commit

Creating good commit messages

Ignoring files

How to merge

Resolving a merge

Getting conflict-resolution help during a merge

Undoing a merge

Fast-forward merges

Fixing mistakes

Fixing a mistake with a new commit
Fixing a mistake by editing history
Checking out an old version of a file

Ensuring good performance

Ensuring reliability

Checking the repository for corruption
Recovering lost changes

Telling git your name

Before creating any commits, you should introduce yourself to git. The +git-hash-object(1) man pages may prove helpful.

ChapterÂ 3.Â Developing with git

Table of Contents

Telling git your name

Creating a new repository

How to make a commit

Creating good commit messages

Ignoring files

How to merge

Resolving a merge

Getting conflict-resolution help during a merge

Undoing a merge

Fast-forward merges

Fixing mistakes

Fixing a mistake with a new commit
Fixing a mistake by editing history
Checking out an old version of a file

Ensuring good performance

Ensuring reliability

Checking the repository for corruption
Recovering lost changes

Telling git your name

Before creating any commits, you should introduce yourself to git. The easiest way to do so is to make sure the following lines appear in a file named .gitconfig in your home directory:

[user]
- name = Your Name Comes Here
- email = you@yourdomain.example.com

(See the "CONFIGURATION FILE" section of 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

Creating a new commit takes three steps:

+Â Â Â Â Â Â Â Â nameÂ =Â YourÂ NameÂ ComesÂ Here
+Â Â Â Â Â Â Â Â emailÂ =Â you@yourdomain.example.com

(See the "CONFIGURATION FILE" section of git-config(1) for +details on the configuration file.)

Creating a new repository

Creating a new repository from scratch is very easy:

$Â mkdirÂ project
+$Â cdÂ project
+$Â gitÂ init

If you have some initial content (say, a tarball):

$Â tarÂ -xzvfÂ project.tar.gz
+$Â cdÂ project
+$Â gitÂ init
+$Â gitÂ addÂ .Â #Â includeÂ everythingÂ belowÂ ./Â inÂ theÂ firstÂ commit:
+$Â gitÂ commit

How to make a commit

Creating a new commit takes three steps:

Making some changes to the working directory using your favorite editor.
@@ -413,22 +413,22 @@ Creating the commit using the content you told git about 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 +that of the HEAD. The command "git diff âcached", 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 +produce no output at that point.
Modifying the index is easy:
To update the index with the new contents of a modified file, use
$Â gitÂ addÂ path/to/file
To add the contents of a new file to the index, use
$Â gitÂ addÂ path/to/file
To remove a file from the index and from the working tree,
$Â gitÂ rmÂ path/to/file
After each step you can verify that
$Â gitÂ diffÂ --cached
always shows the difference between the HEAD and the index fileâthis +is what you'd commit if you created the commit nowâand that
$Â gitÂ 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 -commit. 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 +you run git-add on the file again.
When you're ready, just run
$Â gitÂ commit
and git will prompt you for a commit message and then create the new +commit. Check to make sure it looks like what you expected with
$Â gitÂ show
As a special shortcut,
$Â gitÂ commitÂ -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 diff HEAD     # difference between HEAD and working tree; what
-                    # would be committed if you ran "commit -a" 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 +about to commit:

$Â gitÂ diffÂ --cachedÂ #Â differenceÂ betweenÂ HEADÂ andÂ theÂ index;Â what
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â wouldÂ beÂ committedÂ ifÂ youÂ ranÂ "commit"Â now.
+$Â gitÂ diffÂ Â Â Â Â Â Â Â Â Â #Â differenceÂ betweenÂ theÂ indexÂ fileÂ andÂ your
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â workingÂ directory;Â changesÂ thatÂ wouldÂ not
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â beÂ includedÂ ifÂ youÂ ranÂ "commit"Â now.
+$Â gitÂ diffÂ HEADÂ Â Â Â Â #Â differenceÂ betweenÂ HEADÂ andÂ workingÂ tree;Â what
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â wouldÂ beÂ committedÂ ifÂ youÂ ranÂ "commitÂ -a"Â now.
+$Â gitÂ statusÂ Â Â Â Â Â Â Â #Â aÂ briefÂ per-fileÂ summaryÂ ofÂ theÂ 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 @@ -446,14 +446,14 @@ a list of files which git should ignore. Entries in the list may contain globs to specify multiple files, or may be prefixed by "!" to explicitly include (un-ignore) a previously excluded (ignored) file (i.e. later exclude patterns override earlier ones). The following -example should illustrate such patterns:

# Lines starting with '#' are considered comments.
-# Ignore foo.txt.
+example should illustrate such patterns:

#Â LinesÂ startingÂ withÂ '#'Â areÂ consideredÂ comments.
+#Â IgnoreÂ foo.txt.
foo.txt
-# Ignore (generated) html files,
+#Â IgnoreÂ (generated)Â htmlÂ files,
*.html
-# except foo.html which is maintained by hand.
+#Â exceptÂ foo.htmlÂ whichÂ isÂ maintainedÂ byÂ hand.
!foo.html
-# Ignore objects and archives.
+#Â IgnoreÂ objectsÂ andÂ archives.
*.[oa]

The next question is where to put these exclude patterns so that git can find them. Git looks for exclude patterns in the following files:

.gitignore files in your working tree: @@ -491,14 +491,14 @@ The file specified by the core.excludesfile config

Note

In addition to the above alternatives, there are git commands that can take exclude patterns directly on the command line. See git-ls-files(1) for an example of this.

How to merge

You can rejoin two diverging branches of development using -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 +git-merge(1):

$Â gitÂ mergeÂ branchname

merges the development in the branch "branchname" into the current +branch. If there are conflictsâfor 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 merge next
- 100% (4/4) done
-Auto-merged 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 +branchâthen you are warned; the output may look something like this:

$Â gitÂ mergeÂ next
+Â 100%Â (4/4)Â done
+Auto-mergedÂ file.txt
+CONFLICTÂ (content):Â MergeÂ conflictÂ inÂ file.txt
+AutomaticÂ mergeÂ failed;Â fixÂ conflictsÂ andÂ thenÂ commitÂ theÂ 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 @@ -507,38 +507,38 @@ one to the top of the other branch.

Files with conflicts are marked specially in the index, so until you resolve the problem and update the index, git-commit(1) will -fail:

$ git commit
-file.txt: needs merge

Also, git-status(1) will list those files as "unmerged", and the -files with conflicts will have conflict markers added, like this:

<<<<<<< HEAD:file.txt
-Hello world
+fail:

$Â gitÂ commit
+file.txt:Â needsÂ merge

Also, git-status(1) will list those files as "unmerged", and the +files with conflicts will have conflict markers added, like this:

<<<<<<<Â HEAD:file.txt
+HelloÂ world
=======
Goodbye
->>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt

All you need to do is edit the files to resolve the conflicts, and then

$ git add file.txt
-$ git commit

Note that the commit message will already be filled in for you with +>>>>>>>Â 77976da35a11db4580b80ae27e8d65caf5208086:file.txt

All you need to do is edit the files to resolve the conflicts, and then

$Â gitÂ addÂ file.txt
+$Â gitÂ 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.

The above is all you need to know to resolve a simple merge. But git also provides more information to help resolve conflicts:

Getting conflict-resolution help during a merge

All of the changes that git was able to merge automatically are already added to the index file, so git-diff(1) shows only -the conflicts. It uses an 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
+the conflicts. It uses an unusual syntax:

$Â gitÂ diff
+diffÂ --ccÂ file.txt
+indexÂ 802992c,2b60207..0000000
+---Â a/file.txt
++++Â b/file.txt
+@@@Â -1,1Â -1,1Â +1,5Â @@@
+++<<<<<<<Â HEAD:file.txt
+Â +HelloÂ world
++=======
-+ Goodbye
-++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt

Recall that the commit which will be commited after we resolve this ++Â Goodbye
+++>>>>>>>Â 77976da35a11db4580b80ae27e8d65caf5208086:file.txt

Recall that the commit which will be committed 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.

During the merge, the index holds three versions of each file. Each of -these three "file stages" represents a different version of the file:

$ git show :1:file.txt  # the file in a common ancestor of both branches
-$ git show :2:file.txt  # the version from HEAD, but including any
-                        # nonconflicting changes from MERGE_HEAD
-$ git show :3:file.txt  # the version from MERGE_HEAD, but including any
-                        # nonconflicting changes from HEAD.

Since the stage 2 and stage 3 versions have already been updated with +these three "file stages" represents a different version of the file:

$Â gitÂ showÂ :1:file.txtÂ Â #Â theÂ fileÂ inÂ aÂ commonÂ ancestorÂ ofÂ bothÂ branches
+$Â gitÂ showÂ :2:file.txtÂ Â #Â theÂ versionÂ fromÂ HEAD,Â butÂ includingÂ any
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â nonconflictingÂ changesÂ fromÂ MERGE_HEAD
+$Â gitÂ showÂ :3:file.txtÂ Â #Â theÂ versionÂ fromÂ MERGE_HEAD,Â butÂ includingÂ any
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â nonconflictingÂ changesÂ fromÂ HEAD.

Since the stage 2 and stage 3 versions have already been updated with nonconflicting changes, the only remaining differences between them are the important ones; thus git-diff(1) can use the information in the index to show only those conflicts.

The diff above shows the differences between the working-tree version of @@ -548,41 +548,41 @@ 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. (See the "COMBINED DIFF FORMAT" section of git-diff-files(1) for a details of the format.)

After resolving the conflict in the obvious way (but before updating the -index), 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 +index), the diff will look like:

$Â gitÂ diff
+diffÂ --ccÂ file.txt
+indexÂ 802992c,2b60207..0000000
+---Â a/file.txt
++++Â b/file.txt
+@@@Â -1,1Â -1,1Â +1,1Â @@@
+-Â HelloÂ world
+Â -Goodbye
+++GoodbyeÂ 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.

Some special diff options allow diffing the working directory against -any of these stages:

$ git diff -1 file.txt          # diff against stage 1
-$ git diff --base file.txt      # same as the above
-$ git diff -2 file.txt          # diff against stage 2
-$ git diff --ours file.txt      # same as the above
-$ git diff -3 file.txt          # diff against stage 3
-$ git diff --theirs file.txt    # same as the above.

The git-log(1) and gitk[1] commands also provide special help -for merges:

$ git log --merge
-$ gitk --merge

These will display all commits which exist only on HEAD or on +any of these stages:

$Â gitÂ diffÂ -1Â file.txtÂ Â Â Â Â Â Â Â Â Â #Â diffÂ againstÂ stageÂ 1
+$Â gitÂ diffÂ --baseÂ file.txtÂ Â Â Â Â Â #Â sameÂ asÂ theÂ above
+$Â gitÂ diffÂ -2Â file.txtÂ Â Â Â Â Â Â Â Â Â #Â diffÂ againstÂ stageÂ 2
+$Â gitÂ diffÂ --oursÂ file.txtÂ Â Â Â Â Â #Â sameÂ asÂ theÂ above
+$Â gitÂ diffÂ -3Â file.txtÂ Â Â Â Â Â Â Â Â Â #Â diffÂ againstÂ stageÂ 3
+$Â gitÂ diffÂ --theirsÂ file.txtÂ Â Â Â #Â sameÂ asÂ theÂ above.

The git-log(1) and gitk[1] commands also provide special help +for merges:

$Â gitÂ logÂ --merge
+$Â gitkÂ --merge

These will display all commits which exist only on HEAD or on MERGE_HEAD, and which touch an unmerged file.

You may also use git-mergetool(1), which lets you merge the -unmerged files using external tools such as emacs or kdiff3.

Each time you resolve the conflicts in a file and update the index:

$ git add file.txt

the different stages of that file will be "collapsed", after which +unmerged files using external tools such as emacs or kdiff3.

Each time you resolve the conflicts in a file and update the index:

$Â gitÂ addÂ file.txt

the different stages of that file will be "collapsed", after which git-diff will (by default) no longer show diffs for that file.

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 ORIG_HEAD

However, this last command can be dangerous in some cases—never +away, you can always return to the pre-merge state with

$Â gitÂ resetÂ --hardÂ HEAD

Or, if you've already committed the merge that you want to throw away,

$Â gitÂ resetÂ --hardÂ ORIG_HEAD

However, this last command can be dangerous in some casesânever 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 the current branch is a descendant of the other—so every -commit present in the one is already contained in the other—then git +were merged.

However, if the current branch is a descendant of the otherâso every +commit present in the one is already contained in the otherâthen git just performs a "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 +state with

$Â gitÂ resetÂ --hardÂ HEAD

If you make a commit that you later wish you hadn't, there are two fundamentally different ways to fix the problem:

You can create a new commit that undoes whatever was done by the previous commit. This is the correct thing if your @@ -595,57 +595,57 @@ You can go back and modify the old commit. You should 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 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 +commit; for example, to revert the most recent commit:

$Â gitÂ revertÂ 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:

$Â gitÂ revertÂ 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.

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 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 create a new commit, then run

$ git commit --amend

which will replace the old commit by a new commit incorporating your +mistake, just as if you were going to create a new commit, then run

$Â gitÂ commitÂ --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 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 -another chapter.

Checking out an old version of a file

In the process of undoing a previous bad change, you may find it +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 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 +name: the command

$Â gitÂ checkoutÂ HEAD^Â 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 -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 +git-show(1):

$Â gitÂ showÂ 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 git-gc(1):

$ git gc

to recompress the archive. This can be very time-consuming, so +should occasionally run git-gc(1):

$Â gitÂ 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 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
+time. The most common warning by far is about "dangling" objects:

$Â gitÂ fsck
+danglingÂ commitÂ 7281251ddd2a61e38657c827739c57015671a6b3
+danglingÂ commitÂ 2706a059f258c6b245f298dc4ff2ccd30ec21a63
+danglingÂ commitÂ 13472b7c4b80851a1bc551779171dcb03655e9b5
+danglingÂ blobÂ 218761f9d90712d37a9c5e36f406f92202db07eb
+danglingÂ commitÂ bf093535a34a4d35731aa2bd90fe6b176302f14f
+danglingÂ commitÂ 8e4bec7f2ddaa268bef999853c25755452100f8e
+danglingÂ treeÂ d50bb86186bf27b681d25af89d3b5b68382e4085
+danglingÂ treeÂ b24c2473f1fd3d91352a624795be026d64c8841f
...

Dangling objects are not a problem. At worst they may take up a little extra disk space. They can sometimes provide a last-resort method for -recovering lost work—see the section called “Dangling objects” for details. However, if -you wish, you can remove them with git-prune(1) or the —prune -option to git-gc(1):

$ git gc --prune

This may be time-consuming. Unlike most other git operations (including +recovering lost workâsee the section called âDangling objectsâ for details. However, if +you wish, you can remove them with git-prune(1) or the âprune +option to git-gc(1):

$Â gitÂ gcÂ --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.

Recovering lost changes

Reflogs

Say you modify a branch with git-reset(1) —hard, and then +other git operations are in progress in the same repository.

Recovering lost changes

Reflogs

Say you modify a branch with git-reset(1) âhard, 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. +old history using, for example,

$Â gitÂ logÂ 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
-$ git log --walk-reflogs master # show reflog entries for master

A separate reflog is kept for the HEAD, so

$ git show HEAD@{"1 week ago"}

will show what HEAD pointed to one week ago, not what the current branch +not just with git log. Some other examples:

$Â gitÂ showÂ master@{2}Â Â Â Â Â Â Â Â Â Â Â #Â SeeÂ whereÂ theÂ branchÂ pointedÂ 2,
+$Â gitÂ showÂ master@{3}Â Â Â Â Â Â Â Â Â Â Â #Â 3,Â ...Â changesÂ ago.
+$Â gitkÂ master@{yesterday}Â Â Â Â Â Â Â #Â SeeÂ whereÂ itÂ pointedÂ yesterday,
+$Â gitkÂ master@{"1Â weekÂ ago"}Â Â Â Â #Â ...Â orÂ lastÂ week
+$Â gitÂ logÂ --walk-reflogsÂ masterÂ #Â showÂ reflogÂ entriesÂ forÂ master

A separate reflog is kept for the HEAD, so

$Â gitÂ showÂ HEAD@{"1Â weekÂ ago"}

will show what HEAD pointed to one week ago, not what the current branch pointed to one week ago. This allows you to see the history of what you've checked out.

The reflogs are kept by default for 30 days, after which they may be pruned. See git-reflog(1) and git-gc(1) to learn @@ -658,41 +658,41 @@ suppose you delete a branch, then realize you need the history it contained. 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 in the dangling objects that git-fsck reports. See -the section called “Dangling objects” for the details.

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 +one of those dangling commits with, for example,

$Â gitkÂ 7281251dddÂ --notÂ --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 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

Other types of dangling objects (blobs and trees) are also possible, and -dangling objects can arise in other situations.

Chapter 4. Sharing development with others

Table of Contents

Getting updates with git pull

Submitting patches to a project

Importing patches to a project

Public git repositories

Setting up a public repository
Exporting a git repository via the git protocol
Exporting a git repository via http
Pushing changes to a public repository
Setting up a shared repository
Allowing web browsing of a repository

Examples

Maintaining topic branches for a Linux subsystem maintainer

Getting updates with git pull

After you clone a repository and make a few changes of your own, you +reference pointing to it, for example, a new branch:

$Â gitÂ branchÂ recovered-branchÂ 7281251ddd

Other types of dangling objects (blobs and trees) are also possible, and +dangling objects can arise in other situations.

ChapterÂ 4.Â Sharing development with others

Table of Contents

Getting updates with git pull

Submitting patches to a project

Importing patches to a project

Public git repositories

Setting up a public repository
Exporting a git repository via the git protocol
Exporting a git repository via http
Pushing changes to a public repository
Setting up a shared repository
Allowing web browsing of a repository

Examples

Maintaining topic branches for a Linux subsystem maintainer

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 how to keep remote tracking branches up to date with 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 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, +original repository's master branch with:

$Â gitÂ fetch
+$Â gitÂ mergeÂ origin/master

However, the git-pull(1) command provides a way to do this in +one step:

$Â gitÂ pullÂ originÂ 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 +so often you can accomplish the above with just

$Â gitÂ pull

See the descriptions of the branch.<name>.remote and branch.<name>.merge options in git-config(1) to learn how to control these defaults -depending on the current branch. Also note that the —track option to +depending on the current branch. Also note that the âtrack option to git-branch(1) and git-checkout(1) can be used to automatically set the default remote branch to pull from at the time -that a branch is created:

$ git checkout --track -b maint origin/maint

In addition to saving you keystrokes, "git pull" also helps you by +that a branch is created:

$Â gitÂ checkoutÂ --trackÂ -bÂ maintÂ origin/maint

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 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 git-format-patch(1); for example:

$ git format-patch origin

will produce a numbered series of files in the current directory, one +the commands

$Â gitÂ pullÂ .Â branch
+$Â gitÂ mergeÂ 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 git-format-patch(1); for example:

$Â gitÂ format-patchÂ 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 git-send-email(1) script to automate the process. @@ -700,12 +700,12 @@ 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 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 +single mailbox file, say "patches.mbox", then run

$Â gitÂ amÂ -3Â 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". (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 +resolution, instead of creating a new commit, just run

$Â gitÂ amÂ --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.

Public git repositories

Another way to submit changes to a project is to tell the maintainer of @@ -714,8 +714,8 @@ In the section "

$ git clone /path/to/repository
-$ git pull /path/to/other/repository

or an ssh url:

$ git clone ssh://yourhost/~you/repository

For projects with few developers, or for synchronizing a few private +local directory name:

$Â gitÂ cloneÂ /path/to/repository
+$Â gitÂ pullÂ /path/to/other/repository

or an ssh url:

$Â gitÂ cloneÂ ssh://yourhost/~you/repository

For projects with few developers, or for synchronizing a few private repositories, this may be all you need.

However, the more common way to do this is to maintain a separate public repository (usually on a different host) for others to pull changes from. This is usually more convenient, and allows you to cleanly @@ -734,8 +734,8 @@ your personal repo ------------------> your public repo | they push V their public repo <------------------- their repo

We explain how to do this in the following sections.

Setting up a public repository

Assume your personal repository is in the directory ~/proj. We first create a new clone of the repository and tell git-daemon that it -is meant to be public:

$ git clone --bare ~/proj proj.git
-$ touch proj.git/git-daemon-export-ok

The resulting directory proj.git contains a "bare" git repository—it is +is meant to be public:

$Â gitÂ cloneÂ --bareÂ ~/projÂ proj.git
+$Â touchÂ proj.git/git-daemon-export-ok

The resulting directory proj.git contains a "bare" git repositoryâit is just the contents of the ".git" directory, without any files checked out around it.

Next, copy proj.git to the server where you plan to host the public repository. You can use scp, rsync, or whatever is most @@ -751,13 +751,13 @@ arguments will further restrict the exports to those paths.

You can also r examples section.)

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 --bare update-server-info
-$ chmod a+x hooks/post-update

(For an explanation of the last two lines, see +adjustments to give web clients some extra information they need:

$Â mvÂ proj.gitÂ /home/you/public_html/proj.git
+$Â cdÂ proj.git
+$Â gitÂ --bareÂ update-server-info
+$Â chmodÂ a+xÂ hooks/post-update

(For an explanation of the last two lines, see git-update-server-info(1), and the documentation 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 +clone or pull from that url, for example with a commandline like:

$Â gitÂ cloneÂ http://yourserver.com/~you/proj.git

(See also setup-git-server-over-http for a slightly more sophisticated setup using WebDAV which also allows pushing over http.)

Pushing changes to a public repository

Note that the two techniques outlined above (exporting via @@ -766,19 +766,19 @@ 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 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 +branch named "master", run

$Â gitÂ pushÂ ssh://yourserver.com/~you/proj.gitÂ master:master

or just

$Â gitÂ pushÂ ssh://yourserver.com/~you/proj.gitÂ master

As with git-fetch, git-push will complain if this does not result in a 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

Note that the target of a "push" is normally a +proceeding the branch name by a plus sign:

$Â gitÂ pushÂ ssh://yourserver.com/~you/proj.gitÂ +master

Note that the target of a "push" is normally a bare repository. You can also push to a repository that has a checked-out working tree, but the working tree will not be updated by the push. This may lead to unexpected results if the branch you push to is the currently checked-out branch!

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, +save typing; so, for example, after

$Â catÂ >>.git/configÂ <<EOF
+[remoteÂ "public-repo"]
+Â Â Â Â Â Â Â Â urlÂ =Â ssh://yourserver.com/~you/proj.git
+EOF

you should be able to perform the above push with just

$Â gitÂ pushÂ public-repoÂ master

See the explanations of the remote.<name>.url, branch.<name>.remote, and remote.<name>.push options in 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 @@ -786,8 +786,8 @@ all push to and pull from a single shared repository. See git for CVS users for instructions on how to set this up.

However, while there is nothing wrong with git's support for shared repositories, this mode of operation is not generally recommended, -simply because the mode of collaboration that git supports—by -exchanging patches and pulling from public repositories—has so many +simply because the mode of collaboration that git supportsâby +exchanging patches and pulling from public repositoriesâhas so many advantages over the central shared repository:

Git's ability to quickly import and merge patches allows a single maintainer to process incoming changes even at very @@ -819,16 +819,16 @@ A "release" tree into which tested patches are moved for final sanity him a "please pull" request.)

He also uses a set of temporary branches ("topic branches"), each containing a logical grouping of patches.

To set this up, first create your work tree by cloning Linus's public -tree:

$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git work
-$ cd work

Linus's tree will be stored in the remote branch named origin/master, +tree:

$Â gitÂ cloneÂ git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.gitÂ work
+$Â cdÂ work

Linus's tree will be stored in the remote branch named origin/master, and can be updated using git-fetch(1); you can track other public trees using git-remote(1) to set up a "remote" and -git-fetch[1] to keep them up-to-date; see Chapter 1, Repositories and Branches.

Now create the branches in which you are going to work; these start out +git-fetch[1] to keep them up-to-date; see ChapterÂ 1, Repositories and Branches.

Now create the branches in which you are going to work; these start out at the current tip of origin/master branch, and should be set up (using -the —track option to git-branch(1)) to merge changes in from -Linus by default.

$ git branch --track test origin/master
-$ git branch --track release origin/master

These can be easily kept up to date using git-pull(1)

$ git checkout test && git pull
-$ git checkout release && git pull

Important note! If you have any local changes in these branches, then +the âtrack option to git-branch(1)) to merge changes in from +Linus by default.

$Â gitÂ branchÂ --trackÂ testÂ origin/master
+$Â gitÂ branchÂ --trackÂ releaseÂ origin/master

These can be easily kept up to date using git-pull(1)

$Â gitÂ checkoutÂ testÂ &&Â gitÂ pull
+$Â gitÂ checkoutÂ releaseÂ &&Â gitÂ pull

Important note! If you have any local changes in these branches, then this merge will create a commit object in the history (with no local changes git will simply do a "Fast forward" merge). Many people dislike the "noise" that this creates in the Linux history, so you should avoid @@ -836,133 +836,133 @@ doing this capriciously in the "release" branch, as these noisy commits will become part of the permanent history when you ask Linus to pull from the release branch.

A few configuration variables (see git-config(1)) can make it easy to push both branches to your public tree. (See -the section called “Setting up a public repository”.)

$ cat >> .git/config <<EOF
-[remote "mytree"]
-        url =  master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
-        push = release
-        push = test
+the section called âSetting up a public repositoryâ.)

$Â catÂ >>Â .git/configÂ <<EOF
+[remoteÂ "mytree"]
+Â Â Â Â Â Â Â Â urlÂ =Â Â master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux-2.6.git
+Â Â Â Â Â Â Â Â pushÂ =Â release
+Â Â Â Â Â Â Â Â pushÂ =Â test
EOF

Then you can push both the test and release trees using -git-push(1):

$ git push mytree

or push just one of the test and release branches using:

$ git push mytree test

$ git push mytree release

Now to apply some patches from the community. Think of a short +git-push(1):

$Â gitÂ pushÂ mytree

or push just one of the test and release branches using:

$Â gitÂ pushÂ mytreeÂ test

$Â gitÂ pushÂ mytreeÂ release

Now to apply some patches from the community. Think of a short snappy name for a branch to hold this patch (or related group of patches), and create a new branch from the current tip of Linus's -branch:

$ git checkout -b speed-up-spinlocks origin

Now you apply the patch(es), run some tests, and commit the change(s). If +branch:

$Â gitÂ checkoutÂ -bÂ speed-up-spinlocksÂ origin

Now you apply the patch(es), run some tests, and commit the change(s). If the patch is a multi-part series, then you should apply each as a separate -commit to this branch.

$ ... patch ... test ... commit [ ... patch ... test ... commit ]*

When you are happy with the state of this change, you can pull it into the -"test" branch in preparation to make it public:

$ git checkout test && git pull . speed-up-spinlocks

It is unlikely that you would have any conflicts here … but you might if you +commit to this branch.

$Â ...Â patchÂ ...Â testÂ Â ...Â commitÂ [Â ...Â patchÂ ...Â testÂ ...Â commitÂ ]*

When you are happy with the state of this change, you can pull it into the +"test" branch in preparation to make it public:

$Â gitÂ checkoutÂ testÂ &&Â gitÂ pullÂ .Â speed-up-spinlocks

It is unlikely that you would have any conflicts here â¦ but you might if you spent a while on this step and had also pulled new versions from upstream.

Some time later when enough time has passed and testing done, you can pull the same branch into the "release" tree ready to go upstream. This is where you see the value of keeping each patch (or patch series) in its own branch. It -means that the patches can be moved into the "release" tree in any order.

$ git checkout release && git pull . speed-up-spinlocks

After a while, you will have a number of branches, and despite the +means that the patches can be moved into the "release" tree in any order.

$Â gitÂ checkoutÂ releaseÂ &&Â gitÂ pullÂ .Â speed-up-spinlocks

After a while, you will have a number of branches, and despite the well chosen names you picked for each of them, you may forget what they are for, or what status they are in. To get a reminder of what -changes are in a specific branch, use:

$ git log linux..branchname | git-shortlog

To see whether it has already been merged into the test or release branches -use:

$ git log test..branchname

$ git log release..branchname

(If this branch has not yet been merged you will see some log entries. +changes are in a specific branch, use:

$Â gitÂ logÂ linux..branchnameÂ |Â git-shortlog

To see whether it has already been merged into the test or release branches +use:

$Â gitÂ logÂ test..branchname

$Â gitÂ logÂ release..branchname

(If this branch has not yet been merged you will see some log entries. If it has been merged, then there will be no output.)

Once a patch completes the great cycle (moving from test to release, then pulled by Linus, and finally coming back into your local "origin/master" branch) the branch for this change is no longer needed. -You detect this when the output from:

$ git log origin..branchname

is empty. At this point the branch can be deleted:

$ git branch -d branchname

Some changes are so trivial that it is not necessary to create a separate +You detect this when the output from:

$Â gitÂ logÂ origin..branchname

is empty. At this point the branch can be deleted:

$Â gitÂ branchÂ -dÂ branchname

Some changes are so trivial that it is not necessary to create a separate branch and then merge into each of the test and release branches. For these changes, just apply directly to the "release" branch, and then merge that into the "test" branch.

To create diffstat and shortlog summaries of changes to include in a "please -pull" request to Linus you can use:

$ git diff --stat origin..release

and

$ git log -p origin..release | git shortlog

Here are some of the scripts that simplify all this even further.

==== update script ====
-# Update a branch in my GIT tree. If the branch to be updated
-# is origin, then pull from kernel.org. Otherwise merge
-# origin/master branch into test|release branch
+pull" request to Linus you can use:

$Â gitÂ diffÂ --statÂ origin..release

and

$Â gitÂ logÂ -pÂ origin..releaseÂ |Â gitÂ shortlog

Here are some of the scripts that simplify all this even further.

====Â updateÂ scriptÂ ====
+#Â UpdateÂ aÂ branchÂ inÂ myÂ GITÂ tree.Â Â IfÂ theÂ branchÂ toÂ beÂ updated
+#Â isÂ origin,Â thenÂ pullÂ fromÂ kernel.org.Â Â OtherwiseÂ merge
+#Â origin/masterÂ branchÂ intoÂ test|releaseÂ branch

-case "$1" in
+caseÂ "$1"Â in
test|release)
-        git checkout $1 && git pull . origin
-        ;;
+Â Â Â Â Â Â Â Â gitÂ checkoutÂ $1Â &&Â gitÂ pullÂ .Â origin
+Â Â Â Â Â Â Â Â ;;
origin)
-        before=$(cat .git/refs/remotes/origin/master)
-        git fetch origin
-        after=$(cat .git/refs/remotes/origin/master)
-        if [ $before != $after ]
-        then
-                git log $before..$after | git shortlog
-        fi
-        ;;
+Â Â Â Â Â Â Â Â before=$(catÂ .git/refs/remotes/origin/master)
+Â Â Â Â Â Â Â Â gitÂ fetchÂ origin
+Â Â Â Â Â Â Â Â after=$(catÂ .git/refs/remotes/origin/master)
+Â Â Â Â Â Â Â Â ifÂ [Â $beforeÂ !=Â $afterÂ ]
+Â Â Â Â Â Â Â Â then
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â gitÂ logÂ $before..$afterÂ |Â gitÂ shortlog
+Â Â Â Â Â Â Â Â fi
+Â Â Â Â Â Â Â Â ;;
*)
-        echo "Usage: $0 origin|test|release" 1>&2
-        exit 1
-        ;;
-esac

==== merge script ====
-# Merge a branch into either the test or release branch
+Â Â Â Â Â Â Â Â echoÂ "Usage:Â $0Â origin|test|release"Â 1>&2
+Â Â Â Â Â Â Â Â exitÂ 1
+Â Â Â Â Â Â Â Â ;;
+esac

====Â mergeÂ scriptÂ ====
+#Â MergeÂ aÂ branchÂ intoÂ eitherÂ theÂ testÂ orÂ releaseÂ branch

pname=$0

usage()
{
-        echo "Usage: $pname branch test|release" 1>&2
-        exit 1
+Â Â Â Â Â Â Â Â echoÂ "Usage:Â $pnameÂ branchÂ test|release"Â 1>&2
+Â Â Â Â Â Â Â Â exitÂ 1
}

-if [ ! -f .git/refs/heads/"$1" ]
+ifÂ [Â !Â -fÂ .git/refs/heads/"$1"Â ]
then
-        echo "Can't see branch <$1>" 1>&2
-        usage
+Â Â Â Â Â Â Â Â echoÂ "Can'tÂ seeÂ branchÂ <$1>"Â 1>&2
+Â Â Â Â Â Â Â Â usage
fi

-case "$2" in
+caseÂ "$2"Â in
test|release)
-        if [ $(git log $2..$1 | wc -c) -eq 0 ]
-        then
-                echo $1 already merged into $2 1>&2
-                exit 1
-        fi
-        git checkout $2 && git pull . $1
-        ;;
+Â Â Â Â Â Â Â Â ifÂ [Â $(gitÂ logÂ $2..$1Â |Â wcÂ -c)Â -eqÂ 0Â ]
+Â Â Â Â Â Â Â Â then
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ $1Â alreadyÂ mergedÂ intoÂ $2Â 1>&2
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â exitÂ 1
+Â Â Â Â Â Â Â Â fi
+Â Â Â Â Â Â Â Â gitÂ checkoutÂ $2Â &&Â gitÂ pullÂ .Â $1
+Â Â Â Â Â Â Â Â ;;
*)
-        usage
-        ;;
-esac

==== status script ====
-# report on status of my ia64 GIT tree
+Â Â Â Â Â Â Â Â usage
+Â Â Â Â Â Â Â Â ;;
+esac

====Â statusÂ scriptÂ ====
+#Â reportÂ onÂ statusÂ ofÂ myÂ ia64Â GITÂ tree

-gb=$(tput setab 2)
-rb=$(tput setab 1)
-restore=$(tput setab 9)
+gb=$(tputÂ setabÂ 2)
+rb=$(tputÂ setabÂ 1)
+restore=$(tputÂ setabÂ 9)

-if [ `git rev-list test..release | wc -c` -gt 0 ]
+ifÂ [Â `gitÂ rev-listÂ test..releaseÂ |Â wcÂ -c`Â -gtÂ 0Â ]
then
-        echo $rb Warning: commits in release that are not in test $restore
-        git log test..release
+Â Â Â Â Â Â Â Â echoÂ $rbÂ Warning:Â commitsÂ inÂ releaseÂ thatÂ areÂ notÂ inÂ testÂ $restore
+Â Â Â Â Â Â Â Â gitÂ logÂ test..release
fi

-for branch in `ls .git/refs/heads`
+forÂ branchÂ inÂ `lsÂ .git/refs/heads`
do
-        if [ $branch = test -o $branch = release ]
-        then
-                continue
-        fi
+Â Â Â Â Â Â Â Â ifÂ [Â $branchÂ =Â testÂ -oÂ $branchÂ =Â releaseÂ ]
+Â Â Â Â Â Â Â Â then
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â continue
+Â Â Â Â Â Â Â Â fi

-        echo -n $gb ======= $branch ====== $restore " "
-        status=
-        for ref in test release origin/master
-        do
-                if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
-                then
-                        status=$status${ref:0:1}
-                fi
-        done
-        case $status in
-        trl)
-                echo $rb Need to pull into test $restore
-                ;;
-        rl)
-                echo "In test"
-                ;;
-        l)
-                echo "Waiting for linus"
-                ;;
-        "")
-                echo $rb All done $restore
-                ;;
-        *)
-                echo $rb "<$status>" $restore
-                ;;
-        esac
-        git log origin/master..$branch | git shortlog
-done

Chapter 5. Rewriting history and maintaining patch series

Table of Contents

Creating the perfect patch series
Keeping a patch series up to date using git-rebase
Modifying a single commit
Reordering or selecting from a patch series
Other tools
Problems with rewriting history

Normally commits are only added to a project, never taken away or +Â Â Â Â Â Â Â Â echoÂ -nÂ $gbÂ =======Â $branchÂ ======Â $restoreÂ "Â "
+Â Â Â Â Â Â Â Â status=
+Â Â Â Â Â Â Â Â forÂ refÂ inÂ testÂ releaseÂ origin/master
+Â Â Â Â Â Â Â Â do
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ifÂ [Â `gitÂ rev-listÂ $ref..$branchÂ |Â wcÂ -c`Â -gtÂ 0Â ]
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â then
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â status=$status${ref:0:1}
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â fi
+Â Â Â Â Â Â Â Â done
+Â Â Â Â Â Â Â Â caseÂ $statusÂ in
+Â Â Â Â Â Â Â Â trl)
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ $rbÂ NeedÂ toÂ pullÂ intoÂ testÂ $restore
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ;;
+Â Â Â Â Â Â Â Â rl)
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ "InÂ test"
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ;;
+Â Â Â Â Â Â Â Â l)
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ "WaitingÂ forÂ linus"
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ;;
+Â Â Â Â Â Â Â Â "")
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ $rbÂ AllÂ doneÂ $restore
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ;;
+Â Â Â Â Â Â Â Â *)
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â echoÂ $rbÂ "<$status>"Â $restore
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ;;
+Â Â Â Â Â Â Â Â esac
+Â Â Â Â Â Â Â Â gitÂ logÂ origin/master..$branchÂ |Â gitÂ shortlog
+done

ChapterÂ 5.Â Rewriting history and maintaining patch series

Table of Contents

Creating the perfect patch series
Keeping a patch series up to date using git-rebase
Modifying a single commit
Reordering or selecting from a patch series
Other tools
Problems with rewriting history

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 @@ -985,11 +985,11 @@ The complete series produces the same end result as your own

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 that you create a branch "mywork" on a remote-tracking branch -"origin", and create some commits on top of it:

$ git checkout -b mywork origin
-$ vi file.txt
-$ git commit
-$ vi otherfile.txt
-$ git commit
+"origin", and create some commits on top of it:

$Â gitÂ checkoutÂ -bÂ myworkÂ origin
+$Â viÂ file.txt
+$Â gitÂ commit
+$Â viÂ otherfile.txt
+$Â gitÂ 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
         \
@@ -1001,8 +1001,8 @@ the result would create a new merge commit, like this:
git-rebase(1):
$ git checkout mywork

-$ git rebase origin
This will remove each of your commits from mywork, temporarily saving
+git-rebase(1):
$Â gitÂ checkoutÂ mywork

+$Â gitÂ rebaseÂ 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
@@ -1010,29 +1010,29 @@ patches to the new mywork.  The result will look like:
$ 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

Modifying a single commit

We saw in the section called “Fixing a mistake by editing history” that you can replace the -most recent commit using

$ git commit --amend

which will replace the old commit by a new commit incorporating your +running git-commit, just run

$Â gitÂ rebaseÂ --continue

and git will continue applying the rest of the patches.

At any point you may use the âabort option to abort this process and +return mywork to the state it had before you started the rebase:

$Â gitÂ rebaseÂ --abort

Modifying a single commit

We saw in the section called âFixing a mistake by editing historyâ that you can replace the +most recent commit using

$Â gitÂ commitÂ --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.

You can also use a combination of this and git-rebase(1) to edit -commits further back in your history. First, tag the problematic commit with

$ git tag bad mywork~5

(Either gitk or git-log may be useful for finding the commit.)

Then check out that commit, edit it, and rebase the rest of the series +commits further back in your history. First, tag the problematic commit with

$Â gitÂ tagÂ badÂ mywork~5

(Either gitk or git-log may be useful for finding the commit.)

Then check out that commit, edit it, and rebase the rest of the series on top of it (note that we could check out the commit on a temporary -branch, but instead we're using a detached head):

$ git checkout bad
-$ # make changes here and update the index
-$ git commit --amend
-$ git rebase --onto HEAD bad mywork

When you're done, you'll be left with mywork checked out, with the top +branch, but instead we're using a detached head):

$Â gitÂ checkoutÂ bad
+$Â #Â makeÂ changesÂ hereÂ andÂ updateÂ theÂ index
+$Â gitÂ commitÂ --amend
+$Â gitÂ rebaseÂ --ontoÂ HEADÂ badÂ mywork

When you're done, you'll be left with mywork checked out, with the top patches on mywork reapplied on top of your modified commit. You can -then clean up with

$ git tag -d bad

Note that the immutable nature of git history means that you haven't really +then clean up with

$Â gitÂ tagÂ -dÂ bad

Note that the immutable nature of git history means that you haven't really "modified" existing commits; instead, you have replaced the old commits with new commits having new object names.

Reordering or selecting from a patch series

Given one existing commit, the 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, +series of patches on top of "origin", you might do something like:

$Â gitÂ checkoutÂ -bÂ mywork-newÂ origin
+$Â gitkÂ origin..myworkÂ &

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 +âamend.

Another technique is to use git-format-patch to create a series of +patches, then reset the state to before the patches:

$Â gitÂ format-patchÂ origin
+$Â gitÂ resetÂ --hardÂ origin

Then modify, reorder, or eliminate patches as preferred before applying them again with 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 outside of the scope of this manual.

Problems with rewriting history

The primary problem with rewriting the history of a branch has to do @@ -1056,12 +1056,12 @@ new. The results are likely to be unexpected.

You may still choose to pub 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.

Chapter 6. Advanced branch management

Table of Contents

Fetching individual branches
git fetch and fast-forwards
Forcing git fetch to do non-fast-forward updates
Configuring remote branches

Fetching individual branches

Instead of using git-remote(1), you can also choose just +published branches should never be rewritten.

ChapterÂ 6.Â Advanced branch management

Table of Contents

Fetching individual branches
git fetch and fast-forwards
Forcing git fetch to do non-fast-forward updates
Configuring remote branches

Fetching individual branches

Instead of using 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 +arbitrary name:

$Â gitÂ fetchÂ originÂ 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 +store it locally under the name refs/heads/my-todo-work.

You can also fetch branches from other repositories; so

$Â gitÂ fetchÂ git://example.com/proj.gitÂ 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 @@ -1081,12 +1081,12 @@ 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. Alternatively, you can use the "-f" -flag to force updates of all the fetched branches, as in:

$ git fetch -f origin

Be aware that commits that the old version of example/master pointed at +descendant of the old head, you may force the update with:

$Â gitÂ fetchÂ git://example.com/proj.gitÂ +master:refs/remotes/example/master

Note the addition of the "+" sign. Alternatively, you can use the "-f" +flag to force updates of all the fetched branches, as in:

$Â gitÂ fetchÂ -fÂ origin

Be aware that commits that 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 that you originally cloned from. This information is stored in git configuration variables, which you can see using -git-config(1):

$ git config -l
+git-config(1):

$Â gitÂ configÂ -l
core.repositoryformatversion=0
core.filemode=true
core.logallrefupdates=true
@@ -1095,14 +1095,14 @@ 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:refs/remotes/example/master
-$ git fetch example master:refs/remotes/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 +after

$Â gitÂ configÂ remote.example.urlÂ git://example.com/proj.git

then the following two commands will do the same thing:

$Â gitÂ fetchÂ git://example.com/proj.gitÂ master:refs/remotes/example/master
+$Â gitÂ fetchÂ exampleÂ master:refs/remotes/example/master

Even better, if you add one more option:

$Â gitÂ configÂ remote.example.fetchÂ master:refs/remotes/example/master

then the following commands will all do the same thing:

$Â gitÂ fetchÂ git://example.com/proj.gitÂ master:refs/remotes/example/master
+$Â gitÂ fetchÂ exampleÂ master:refs/remotes/example/master
+$Â gitÂ fetchÂ example

You can also add a "+" to force the update each time:

$Â gitÂ configÂ remote.example.fetchÂ +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 git-config(1).

See git-config(1) for more details on the configuration -options mentioned above.

Chapter 7. Git internals

Table of Contents

The Object Database

The "index" aka "Current Directory Cache"

The Workflow

working directory -> index
index -> object database
object database -> index
index -> working directory
Tying it all together

Examining the data

Merging multiple trees

Merging multiple trees, continued

How git stores objects efficiently: pack files

Dangling objects

A birds-eye view of Git's source code

Git depends on two fundamental abstractions: the "object database", and +options mentioned above.

ChapterÂ 7.Â Git internals

Table of Contents

The Object Database

The "index" aka "Current Directory Cache"

The Workflow

working directory -> index
index -> object database
object database -> index
index -> working directory
Tying it all together

Examining the data

Merging multiple trees

Merging multiple trees, continued

How git stores objects efficiently: pack files

Dangling objects

A birds-eye view of Git's source code

Git depends on two fundamental 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 @@ -1214,7 +1214,7 @@ 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 +like GPG/PGP.

To assist in this, git also provides the tag objectâ¦

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 @@ -1264,27 +1264,27 @@ 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 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 +you want to update, like so:

$Â git-update-indexÂ 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 +should use the âremove and âadd flags respectively.

NOTE! A âremove 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 +removed. The only thing âremove 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 +does not exist any more, it will update the index accordingly.

As a special case, you can also do git-update-index ârefresh, 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 +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

$Â 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 +index. Normal operation is just

$Â git-read-treeÂ <sha1Â ofÂ 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 @@ -1293,7 +1293,7 @@ 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 +with

$Â git-checkout-indexÂ 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 @@ -1307,7 +1307,7 @@ 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 +state at the time of the commit, and a list of parents:

$Â git-commit-treeÂ <tree>Â -pÂ <parent>Â [-pÂ <parent2>Â ..]

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 @@ -1315,48 +1315,48 @@ 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.

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 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 +object:

$Â git-cat-fileÂ -tÂ <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

$Â git-cat-fileÂ blob|tree|commit|tagÂ <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 +you can do

$Â git-cat-fileÂ commitÂ 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 @@ -1364,28 +1364,28 @@ can do multiple parents in one go.

To do a three-way merge, you need the t 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 +of two commits with

$Â git-merge-baseÂ <commit1>Â <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 +do with (for example)

$Â git-cat-fileÂ commitÂ <commitname>Â |Â headÂ -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 tree, 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 +you have in your current index anyway).

To do the merge, do

$Â git-read-treeÂ -mÂ -uÂ <origtree>Â <yourtree>Â <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 +other tools before you can write out the result.

You can examine such index state with git-ls-files âunmerged +command. An example:

$Â git-read-treeÂ -mÂ $origÂ HEADÂ $target
+$Â git-ls-filesÂ --unmerged
+100644Â 263414f423d0e4d70dae8fe53fa34614ff3e2860Â 1Â Â Â Â Â Â Â hello.c
+100644Â 06fa6a24256dc7e560efa5687fa84b51f0263c3aÂ 2Â Â Â Â Â Â Â hello.c
+100644Â cc44c73eb783565da5831b4d820c962954019b69Â 3Â Â Â Â Â Â Â hello.c

Each line of the git-ls-files âunmerged 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 @@ -1398,45 +1398,45 @@ above example shows is that file hello.c was change $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, merge, or git's own merge-file, 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
-$ git merge-file hello.c~2 hello.c~1 hello.c~3

This would leave the merge result in hello.c~2 file, along +the blob objects from these three stages yourself, like this:

$Â git-cat-fileÂ blobÂ 263414f...Â >hello.c~1
+$Â git-cat-fileÂ blobÂ 06fa6a2...Â >hello.c~2
+$Â git-cat-fileÂ blobÂ cc44c73...Â >hello.c~3
+$Â gitÂ merge-fileÂ hello.c~2Â hello.c~1Â 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 +merge result for this file is by:

$Â mvÂ -fÂ hello.c~2Â hello.c
+$Â git-update-indexÂ 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 merge -s 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 +stages to temporary files and calls a "merge" script on it:

$Â git-merge-indexÂ git-merge-one-fileÂ hello.c

and that is what higher level git merge -s 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 +lot of objects. Try this on an old project:

$Â gitÂ count-objects
+6930Â objects,Â 47620Â 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 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 +found in technical/pack-format.txt.

To put the loose objects into a pack, just run git repack:

$Â gitÂ repack
+GeneratingÂ pack...
+DoneÂ countingÂ 6020Â objects.
+DeltifyingÂ 6020Â objects.
+Â 100%Â (6020/6020)Â done
+WritingÂ 6020Â objects.
+Â 100%Â (6020/6020)Â done
+TotalÂ 6020,Â writtenÂ 6020Â (deltaÂ 4070),Â reusedÂ 0Â (deltaÂ 0)
+PackÂ pack-3e54ad29d5b2e05838c75df582c65257b8d08e1cÂ created.

You can then run

$Â gitÂ 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 +.git/objects directory or by running

$Â gitÂ count-objects
+0Â objects,Â 0Â kilobytes

Although the object files are gone, any commands that refer to those objects will work exactly as they did before.

The git-gc(1) command performs packing, pruning, and more for you, so is normally the only high-level command you need.

Dangling objects

The 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 -Chapter 5, Rewriting history and maintaining patch series. In that case, the old head of the original +branch, or you have pulled from somebody else who rebased a branchâsee +ChapterÂ 5, Rewriting history and maintaining patch series. In that case, the old head of the original branch still exists, as does everything it pointed to. The branch pointer itself just doesn't, since you replaced it with another one.

There are also other situations that cause dangling objects. For example, a "dangling blob" may arise because you did a "git add" of a @@ -1454,10 +1454,10 @@ up pointing to them, so they end up "dangling" in your repository.

General 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, you can just use:

$ gitk <dangling-commit-sha-goes-here> --not --all

This asks for all the history reachable from the given commit but not +you have, and decide to reset your head to some old dangling state).

For commits, you can just use:

$Â gitkÂ <dangling-commit-sha-goes-here>Â --notÂ --all

This asks for all the history reachable from the given commit but not from any branch, tag, or other reference. If you decide it's something -you want, you can always create a new reference to it, e.g.,

$ git branch recovered-branch <dangling-commit-sha-goes-here>

For blobs and trees, you can't do the same, but you can still 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 +you want, you can always create a new reference to it, e.g.,

$Â gitÂ branchÂ recovered-branchÂ <dangling-commit-sha-goes-here>

For blobs and trees, you can't do the same, but you can still examine +them. You can just do

$Â gitÂ showÂ <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 @@ -1466,7 +1466,7 @@ 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 +state, you can just prune all unreachable objects:

$Â gitÂ 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 @@ -1476,7 +1476,7 @@ 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).

A birds-eye view of Git's source code

It is not always easy for new developers to find their way through Git's source code. This section gives you a little guidance to show where to -start.

A good place to start is with the contents of the initial commit, with:

$ git checkout e83c5163

The initial revision lays the foundation for almost everything git has +start.

A good place to start is with the contents of the initial commit, with:

$Â gitÂ checkoutÂ e83c5163

The initial revision lays the foundation for almost everything git has today, but is small enough to read in one sitting.

Note that terminology has changed since that revision. For example, the README in that revision uses the word "changeset" to describe what we now call a commit.

Also, we do not call it "cache" any more, but "index", however, the @@ -1494,13 +1494,13 @@ structures in cache.h), and that there are just a c (blobs, trees, commits and tags) which inherit their common structure from struct object, which is their first member (and thus, you can cast e.g. (struct object *)commit to achieve the _same_ as &commit->object, i.e. -get at the object name and flags).

Now is a good point to take a break to let this information sink in.

Next step: get familiar with the object naming. Read the section called “Naming commits”. +get at the object name and flags).

Now is a good point to take a break to let this information sink in.

Next step: get familiar with the object naming. Read the section called âNaming commitsâ. There are quite a few ways to name an object (and not only revisions!). All of these are handled in sha1_name.c. Just have a quick look at the function get_sha1(). A lot of the special handling is done by functions like get_sha1_basic() or the likes.

This is just to get you into the groove for the most libified part of Git: -the revision walker.

Basically, the initial version of git log was a shell script:

$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
- LESS=-S ${PAGER:-less}

What does this mean?

git-rev-list is the original version of the revision walker, which +the revision walker.

Basically, the initial version of git log was a shell script:

$Â git-rev-listÂ --prettyÂ $(git-rev-parseÂ --defaultÂ HEADÂ "$@")Â |Â \
+Â Â Â Â Â Â Â Â LESS=-SÂ ${PAGER:-less}

What does this mean?

git-rev-list is the original version of the revision walker, which _always_ printed a list of revisions to stdout. It is still functional, and needs to, since most new Git programs start out as scripts using git-rev-list.

git-rev-parse is not as important any more; it was only used to filter out @@ -1540,17 +1540,17 @@ was around even in the initial commit (it literally went only through some 20 revisions as cat-file.c, was renamed to builtin-cat-file.c when made a builtin, and then saw less than 10 versions).

So, look into builtin-cat-file.c, search for cmd_cat_file() and look what -it does.

        git_config(git_default_config);
-        if (argc != 3)
-                usage("git-cat-file [-t|-s|-e|-p|<type>] <sha1>");
-        if (get_sha1(argv[2], sha1))
-                die("Not a valid object name %s", argv[2]);

Let's skip over the obvious details; the only really interesting part +it does.

Â Â Â Â Â Â Â Â git_config(git_default_config);
+Â Â Â Â Â Â Â Â ifÂ (argcÂ !=Â 3)
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â usage("git-cat-fileÂ [-t|-s|-e|-p|<type>]Â <sha1>");
+Â Â Â Â Â Â Â Â ifÂ (get_sha1(argv[2],Â sha1))
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â die("NotÂ aÂ validÂ objectÂ nameÂ %s",Â argv[2]);

Let's skip over the obvious details; the only really interesting part here is the call to get_sha1(). It tries to interpret argv[2] as an object name, and if it refers to an object which is present in the current repository, it writes the resulting SHA-1 into the variable sha1.

Two things are interesting here:

get_sha1() returns 0 on _success_. This might surprise some new Git hackers, but there is a long tradition in UNIX to return different - negative numbers in case of different errors — and 0 on success. + negative numbers in case of different errors â and 0 on success.
the variable sha1 in the function signature of get_sha1() is unsigned char *, but is actually expected to be a pointer to unsigned @@ -1558,20 +1558,20 @@ the variable sha1 in the function signature of unsigned char *, it is the binary representation, as opposed to the ASCII representation in hex characters, which is passed as char *. -

You will see both of these things throughout the code.

Now, for the meat:

case 0:
- buf = read_object_with_reference(sha1, argv[1], &size, NULL);

This is how you read a blob (actually, not only a blob, but any type of +

You will see both of these things throughout the code.

Now, for the meat:

Â Â Â Â Â Â Â Â caseÂ 0:
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â bufÂ =Â read_object_with_reference(sha1,Â argv[1],Â &size,Â NULL);

This is how you read a blob (actually, not only a blob, but any type of object). To know how the function read_object_with_reference() actually works, find the source code for it (something like git grep read_object_with | grep ":[a-z]" in the git repository), and read -the source.

To find out how the result can be used, just read on in cmd_cat_file():

write_or_die(1, buf, size);

Sometimes, you do not know where to look for a feature. In many such cases, +the source.

To find out how the result can be used, just read on in cmd_cat_file():

Â Â Â Â Â Â Â Â write_or_die(1,Â buf,Â size);

Sometimes, you do not know where to look for a feature. In many such cases, it helps to search through the output of git log, and then git show the corresponding commit.

Example: If you know that there was some test case for git bundle, but do not remember where it was (yes, you _could_ git grep bundle t/, but that -does not illustrate the point!):

$ git log --no-merges t/

In the pager (less), just search for "bundle", go a few lines back, -and see that it is in commit 18449ab0… Now just copy this object name, -and paste it into the command line

$ git show 18449ab0

Voila.

Another example: Find out what to do in order to make some script a -builtin:

$ git log --no-merges --diff-filter=A builtin-*.c

You see, Git is actually the best tool to find out about the source of Git -itself!

Chapter 8. GIT Glossary

+does not illustrate the point!): $Â gitÂ logÂ --no-mergesÂ t/ In the pager (less), just search for "bundle", go a few lines back, +and see that it is in commit 18449ab0â¦ Now just copy this object name, +and paste it into the command line $Â gitÂ showÂ 18449ab0 Voila. Another example: Find out what to do in order to make some script a +builtin: $Â gitÂ logÂ --no-mergesÂ --diff-filter=AÂ builtin-*.c You see, Git is actually the best tool to find out about the source of Git +itself!

ChapterÂ 8.Â GIT Glossary

alternate object database: Via the alternates mechanism, a repository @@ -1893,7 +1893,7 @@ This commit is referred to as a "merge commit", or sometimes just a; 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 + string. With the âpickaxe-all option, it can be used to view the full changeset that introduced or removed, say, a particular line of text. See git-diff(1).
@@ -2011,7 +2011,7 @@ This commit is referred to as a "merge commit", or sometimes just a 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 the —depth option to git-clone(1), and + is created by giving the âdepth option to git-clone(1), and its history can be later deepened with git-fetch(1).
symref @@ -2088,78 +2088,78 @@ This commit is referred to as a "merge commit", or sometimes just a The tree of actual checked out files. The working tree is normally equal to the HEAD plus any local changes that you have made but not yet committed. -

Appendix A. Git Quick Reference

Table of Contents

Creating a new repository
Managing branches
Exploring history
Making changes
Merging
Sharing your changes
Repository maintenance

This is a quick summary of the major commands; the previous chapters -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 local 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 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
+

AppendixÂ A.Â Git Quick Reference

Table of Contents

Creating a new repository
Managing branches
Exploring history
Making changes
Merging
Sharing your changes
Repository maintenance

This is a quick summary of the major commands; the previous chapters +explain how these work in more detail.

Creating a new repository

From a tarball:

$Â tarÂ xzfÂ project.tar.gz
+$Â cdÂ project
+$Â gitÂ init
+InitializedÂ emptyÂ GitÂ repositoryÂ inÂ .git/
+$Â gitÂ addÂ .
+$Â gitÂ commit

From a remote repository:

$Â gitÂ cloneÂ git://example.com/pub/project.git
+$Â cdÂ project

Managing branches

$Â gitÂ branchÂ Â Â Â Â Â Â Â Â #Â listÂ allÂ localÂ branchesÂ inÂ thisÂ repo
+$Â gitÂ checkoutÂ testÂ Â #Â switchÂ workingÂ directoryÂ toÂ branchÂ "test"
+$Â gitÂ branchÂ newÂ Â Â Â Â #Â createÂ branchÂ "new"Â startingÂ atÂ currentÂ HEAD
+$Â gitÂ branchÂ -dÂ newÂ Â #Â deleteÂ branchÂ "new"

Instead of basing new branch on current HEAD (the default), use:

$Â gitÂ branchÂ newÂ testÂ Â Â Â #Â branchÂ namedÂ "test"
+$Â gitÂ branchÂ newÂ v2.6.15Â #Â tagÂ namedÂ v2.6.15
+$Â gitÂ branchÂ newÂ HEAD^Â Â Â #Â commitÂ beforeÂ theÂ mostÂ recent
+$Â gitÂ branchÂ newÂ HEAD^^Â Â #Â commitÂ beforeÂ that
+$Â gitÂ branchÂ newÂ test~10Â #Â tenÂ commitsÂ beforeÂ tipÂ ofÂ branchÂ "test"

Create and switch to a new branch at the same time:

$Â gitÂ checkoutÂ -bÂ newÂ v2.6.15

Update and examine branches from the repository you cloned from:

$Â gitÂ fetchÂ Â Â Â Â Â Â Â Â Â Â Â Â #Â update
+$Â gitÂ branchÂ -rÂ Â Â Â Â Â Â Â Â #Â list
+Â Â origin/master
+Â Â origin/next
+Â Â ...
+$Â gitÂ checkoutÂ -bÂ masterworkÂ origin/master

Fetch a branch from a different repository, and give it a new +name in your repository:

$Â gitÂ fetchÂ git://example.com/project.gitÂ theirbranch:mybranch
+$Â gitÂ fetchÂ git://example.com/project.gitÂ v2.6.15:mybranch

Keep a list of repositories you work with regularly:

$Â gitÂ remoteÂ addÂ exampleÂ git://example.com/project.git
+$Â gitÂ remoteÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â listÂ remoteÂ 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
+$Â gitÂ remoteÂ showÂ exampleÂ Â Â Â Â Â Â #Â getÂ details
+*Â remoteÂ example
+Â Â URL:Â git://example.com/project.git
+Â Â TrackedÂ remoteÂ branches
+Â Â Â Â masterÂ nextÂ ...
+$Â gitÂ fetchÂ exampleÂ Â Â Â Â Â Â Â Â Â Â Â Â #Â updateÂ branchesÂ fromÂ example
+$Â gitÂ branchÂ -rÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â listÂ allÂ remoteÂ branches

Exploring history

$Â gitkÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â visualizeÂ andÂ browseÂ history
+$Â gitÂ logÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â listÂ allÂ commits
+$Â gitÂ logÂ src/Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â ...modifyingÂ src/
+$Â gitÂ logÂ v2.6.15..v2.6.16Â Â #Â ...inÂ v2.6.16,Â notÂ inÂ v2.6.15
+$Â gitÂ logÂ master..testÂ Â Â Â Â Â #Â ...inÂ branchÂ test,Â notÂ inÂ branchÂ master
+$Â gitÂ logÂ test..masterÂ Â Â Â Â Â #Â ...inÂ branchÂ master,Â butÂ notÂ inÂ test
+$Â gitÂ logÂ test...masterÂ Â Â Â Â #Â ...inÂ oneÂ branch,Â notÂ inÂ both
+$Â gitÂ logÂ -S'foo()'Â Â Â Â Â Â Â Â Â #Â ...whereÂ differenceÂ containÂ "foo()"
+$Â gitÂ logÂ --since="2Â weeksÂ ago"
+$Â gitÂ logÂ -pÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â showÂ patchesÂ asÂ well
+$Â gitÂ showÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â mostÂ recentÂ commit
+$Â gitÂ diffÂ v2.6.15..v2.6.16Â #Â diffÂ betweenÂ twoÂ taggedÂ versions
+$Â gitÂ diffÂ v2.6.15..HEADÂ Â Â Â #Â diffÂ withÂ currentÂ head
+$Â gitÂ grepÂ "foo()"Â Â Â Â Â Â Â Â Â Â #Â searchÂ workingÂ directoryÂ forÂ "foo()"
+$Â gitÂ grepÂ v2.6.15Â "foo()"Â Â #Â searchÂ oldÂ treeÂ forÂ "foo()"
+$Â gitÂ showÂ v2.6.15:a.txtÂ Â Â Â #Â lookÂ atÂ oldÂ versionÂ ofÂ a.txt

Search for regressions:

$Â gitÂ bisectÂ start
+$Â gitÂ bisectÂ badÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â currentÂ versionÂ isÂ bad
+$Â gitÂ bisectÂ goodÂ v2.6.13-rc2Â Â Â #Â lastÂ knownÂ goodÂ revision
+Bisecting:Â 675Â revisionsÂ leftÂ toÂ testÂ afterÂ this
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â testÂ here,Â then:
+$Â gitÂ bisectÂ goodÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â ifÂ thisÂ revisionÂ isÂ good,Â or
+$Â gitÂ bisectÂ badÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â ifÂ thisÂ revisionÂ isÂ bad.
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â repeatÂ untilÂ done.

Making changes

Make sure git knows who to blame:

$Â catÂ >>~/.gitconfigÂ <<\EOF
[user]
- name = Your Name Comes Here
- email = you@yourdomain.example.com
+Â Â Â Â Â Â Â Â nameÂ =Â YourÂ NameÂ ComesÂ Here
+Â Â Â Â Â Â Â Â emailÂ =Â 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

Appendix B. Notes and todo list for this manual

This is a work in progress.

The basic requirements: +commit:

$Â gitÂ addÂ a.txtÂ Â Â Â #Â updatedÂ file
+$Â gitÂ addÂ b.txtÂ Â Â Â #Â newÂ file
+$Â gitÂ rmÂ c.txtÂ Â Â Â Â #Â oldÂ file
+$Â gitÂ commit

Or, prepare and create the commit in one step:

$Â gitÂ commitÂ d.txtÂ #Â useÂ latestÂ contentÂ onlyÂ ofÂ d.txt
+$Â gitÂ commitÂ -aÂ Â Â Â #Â useÂ latestÂ contentÂ ofÂ allÂ trackedÂ files

Merging

$Â gitÂ mergeÂ testÂ Â Â #Â mergeÂ branchÂ "test"Â intoÂ theÂ currentÂ branch
+$Â gitÂ pullÂ git://example.com/project.gitÂ master
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â fetchÂ andÂ mergeÂ inÂ remoteÂ branch
+$Â gitÂ pullÂ .Â testÂ Â #Â equivalentÂ toÂ gitÂ mergeÂ test

Sharing your changes

Importing or exporting patches:

$Â gitÂ format-patchÂ origin..HEADÂ #Â formatÂ aÂ patchÂ forÂ eachÂ commit
+Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â #Â inÂ HEADÂ butÂ notÂ inÂ origin
+$Â gitÂ amÂ mboxÂ #Â importÂ patchesÂ fromÂ theÂ mailboxÂ "mbox"

Fetch a branch in a different git repository, then merge into the +current branch:

$Â gitÂ pullÂ git://example.com/project.gitÂ theirbranch

Store the fetched branch into a local branch before merging into the +current branch:

$Â gitÂ pullÂ git://example.com/project.gitÂ theirbranch:mybranch

After creating commits on a local branch, update the remote +branch with your commits:

$Â gitÂ pushÂ ssh://example.com/project.gitÂ mybranch:theirbranch

When remote and local branch are both named "test":

$Â gitÂ pushÂ ssh://example.com/project.gitÂ test

Shortcut version for a frequently used remote repository:

$Â gitÂ remoteÂ addÂ exampleÂ ssh://example.com/project.git
+$Â gitÂ pushÂ exampleÂ test

Repository maintenance

Check for corruption:

$Â gitÂ fsck

Recompress, remove unused cruft:

$Â gitÂ gc

AppendixÂ B.Â 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 diff --git a/user-manual.txt b/user-manual.txt index 14825c641..0071cd070 100644 --- a/user-manual.txt +++ b/user-manual.txt @@ -449,7 +449,7 @@ 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 contents of a file hierarchy, together with "commits" which show the relationships between these snapshots. Git provides extremely flexible and fast tools for exploring the @@ -1070,7 +1070,7 @@ about to commit: ------------------------------------------------- $ git diff --cached # difference between HEAD and the index; what - # would be commited if you ran "commit" now. + # would be committed 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. @@ -1257,7 +1257,7 @@ index 802992c,2b60207..0000000 ++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt ------------------------------------------------- -Recall that the commit which will be commited after we resolve this +Recall that the commit which will be committed 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. @@ -1351,7 +1351,7 @@ 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, +Or, if you've already committed the merge that you want to throw away, ------------------------------------------------- $ git reset --hard ORIG_HEAD -- 2.26.2