Git User's Manual

4. Developing with git

Check whether two branches point at the same history
Find first tagged version including a given fix

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

5. Sharing development with others

Checking the repository for corruption
Recovering lost changes

Getting updates with git pull
Submitting patches to a project
Importing patches to a project
Setting up a public repository
Exporting a git repository via http
Exporting a git repository via the git protocol
Pushing changes to a public repository
Setting up a shared repository
Allow web browsing of a repository
Examples

6. Rewriting history and maintaining patch series

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

7. Advanced branch management

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

8. Git internals

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

9. Glossary of git terms

10. Notes and todo list for this manual

Preface

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

Chapter 1 gives a brief overview of git commands, without any +Git User's Manual

Git User's Manual

Table of Contents

Preface

1. Git Quick Start

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

2. 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 branches from a remote repository

Naming branches, tags, and other references

Updating a repository with git fetch

Fetching branches from other repositories

3. Exploring git history

4. Developing with git

Check whether two branches point at the same history
Find first tagged version including a given fix

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

5. Sharing development with others

Checking the repository for corruption
Recovering lost changes

Getting updates with git pull
Submitting patches to a project
Importing patches to a project
Setting up a public repository
Exporting a git repository via http
Exporting a git repository via the git protocol
Pushing changes to a public repository
Setting up a shared repository
Allow web browsing of a repository
Examples

6. Rewriting history and maintaining patch series

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

7. Advanced branch management

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

8. Git internals

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

9. Glossary of git terms

10. Notes and todo list for this manual

Preface

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

Chapter 1 gives a brief overview of git commands, without any explanation; you may prefer to skip to chapter 2 on a first reading.

Chapters 2 and 3 explain how to fetch and study a project using git—the tools you'd need to build and test a particular version of a software project, to search for regressions, and so on.

Chapter 4 explains how to do development with git, and chapter 5 how to share that development with others.

Further chapters cover more specialized topics.

Comprehensive reference documentation is available through the man -pages. For a command such as "git clone", just use

$ man git-clone

Chapter 1. Git Quick Start

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 following chapters +pages. For a command such as "git clone", just use

$ man git-clone

Chapter 1. Git Quick Start

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 following chapters will explain how these work in more detail.

Creating a new repository

From a tarball:

$ tar xzf project.tar.gz
$ cd project
$ git init
@@ -57,7 +57,7 @@ Bisecting:                                 # 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
+ # repeat until done.

Making changes

Make sure git knows who to blame:

$ cat >~/.gitconfig <<\EOF
[user]
name = Your Name Comes Here
email = you@yourdomain.example.com
@@ -276,7 +276,7 @@ a new stanza:

$ ...

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 3. Exploring git history

Table of Contents

Check whether two branches point at the same history
Find first tagged version including a given fix

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

Chapter 3. Exploring git history

Table of Contents

Check whether two branches point at the same history
Find first tagged version including a given fix

Git is best thought of as a tool for storing the history of a collection of files. It does this by storing compressed snapshots of the contents of a file heirarchy, together with "commits" which show the relationships between these snapshots.

Git provides extremely flexible and fast tools for exploring the @@ -376,7 +376,7 @@ e05db0fd4f31dde7005f075a84f96b360d05984b
$ git rev-list master
e05db0fd4f31dde7005f075a84f96b360d05984b

Or you could recall that the … operator selects all commits contained reachable from either one reference or the other but not -both: so

$ git log origin...master

will return no commits when the two branches are equal.

Find first tagged version including a given fix

Suppose you know that the commit e05db0fd fixed a certain problem. +both: so

$ git log origin...master

will return no commits when the two branches are equal.

Find first tagged version including a given fix

Suppose you know that the commit e05db0fd fixed a certain problem. You'd like to find the earliest tagged release that contains that fix.

Of course, there may be more than one answer—if the history branched after commit e05db0fd, then there could be multiple "earliest" tagged @@ -403,13 +403,13 @@ available
! [v1.5.0-rc2] GIT v1.5.0-rc2
...

then search for a line that looks like

+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
available

Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and -from v1.5.0-rc2, but not from v1.5.0-rc0.

Chapter 4. Developing with git

Table of Contents

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

Checking the repository for corruption
Recovering lost changes

Telling git your name

Before creating any commits, you should introduce yourself to git. The +from v1.5.0-rc2, but not from v1.5.0-rc0.

Chapter 4. Developing with git

Table of Contents

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

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:

$ cat >~/.gitconfig <<\EOF
[user]
name = Your Name Comes Here
email = you@yourdomain.example.com
EOF

(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
+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
@@ -486,7 +486,7 @@ index conflict will have two parents instead of the usual one: one parent will be HEAD, the tip of the current branch; the other will be the tip of the other branch, which is stored temporarily in MERGE_HEAD.

The diff above shows the differences between the working-tree version -of file.txt and two previous version: one version from HEAD, and one +of file.txt and two previous versions: one version from HEAD, and one from MERGE_HEAD. So instead of preceding each line by a single "+" or "-", it now uses two columns: the first column is used for differences between the first parent and the working directory copy, @@ -519,7 +519,7 @@ contained within the other—so every commit present in the one is already contained in the other—then 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 +any new commits being created.

Fixing mistakes

If you've messed up the working tree, but haven't yet committed your mistake, you can return the entire working tree to the last committed state with

$ git reset --hard HEAD

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

@@ -532,7 +532,7 @@ You can go back and modify the old commit. You should git does not normally expect the "history" of a project to change, and cannot correctly perform repeated merges from a branch that has had its history changed. -

Fixing a mistake with a new commit

Creating a new commit that reverts an earlier change is very easy; +

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 @@ -572,7 +572,7 @@ dangling you can remove them at any time 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 git-gc when run without any options), it is not safe to prune while -other git operations are in progress in the same repository.

For more about dangling objects, see the section called “Dangling objects”.

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.

For more about dangling objects, see the section called “Dangling objects”.

Recovering lost changes

Reflogs

Say you modify a branch with git-reset(1) —hard, and then realize that the branch was the only reference you had to that point in history.

Fortunately, git also keeps a log, called a "reflog", of all the previous values of each branch. So in this case you can still find the @@ -587,9 +587,9 @@ how to control this pruning, and see the "SPECIFYING REVISIONS" section of git-rev-parse(1) for details.

Note that the reflog history is very different from normal git history. While normal history is shared by every repository that works on the same project, the reflog history is not shared: it tells you only about -how the branches in your local repository have changed over time.

Examining dangling objects

In some situations the reflog may not be able to save you. For +how the branches in your local repository have changed over time.

Examining dangling objects

In some situations the reflog may not be able to save you. For example, suppose you delete a branch, then realize you need the history -it pointed you. The reflog is also deleted; however, if you have not +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; run git-fsck and watch for output that mentions "dangling commits":

$ git fsck
@@ -603,7 +603,7 @@ history that is described by all your existing branches and tags. Thus you get exactly the history reachable from that commit that is lost. (And notice that it might not be just one commit: we only report the "tip of the line" as being dangling, but there might be a whole deep -and complex commit history that was gotten dropped.)

If you decide you want the history back, you can always create a new +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

Chapter 5. Sharing development with others

Table of Contents

Getting updates with git pull
Submitting patches to a project
Importing patches to a project
Setting up a public repository
Exporting a git repository via http
Exporting a git repository via the git protocol
Pushing changes to a public repository
Setting up a shared repository
Allow web browsing of a repository
Examples

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), @@ -618,7 +618,7 @@ how to control these defaults depending on the current branch.

In addition 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, +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 @@ -642,8 +642,8 @@ taken from the message containing each patch.

Getting updates with git pull".

If you and maintainer both have accounts on the same machine, then then you can just pull changes from each other's repositories -directly; note that all of the command (git-clone(1), -git-fetch[1], git-pull[1], etc.) which accept a URL as an argument +directly; note that all of the commands (git-clone(1), +git-fetch[1], git-pull[1], etc.) that accept a URL as an argument will also accept a local file patch; so, for example, you can use

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

If this sort of setup is inconvenient or impossible, another (more @@ -705,14 +705,14 @@ all push to and pull from a single shared repository. See git for CVS users for instructions on how to set this up.

Allow web browsing of a repository

The gitweb cgi script provides users an easy way to browse your project's files and history without having to install git; see the file -gitweb/README in the git source tree for instructions on setting it up.

Examples

TODO: topic branches, typical roles as in everyday.txt, ?

Chapter 6. Rewriting history and maintaining patch series

Table of Contents

Creating the perfect patch series
Keeping a patch series up to date using git-rebase
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 +gitweb/README in the git source tree for instructions on setting it up.

Examples

TODO: topic branches, typical roles as in everyday.txt, ?

Chapter 6. Rewriting history and maintaining patch series

Table of Contents

Creating the perfect patch series
Keeping a patch series up to date using git-rebase
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 complicated feature, and to present it to the other developers in a way that makes it easy for them to read your changes, verify that they are correct, and understand why you made each change.

If you present all of your changes as a single patch (or commit), they -may find it is too much to digest all at once.

If you present them with the entire history of your work, complete with +may find that it is too much to digest all at once.

If you present them with the entire history of your work, complete with mistakes, corrections, and dead ends, they may be overwhelmed.

So the ideal is usually to produce a series of patches such that:

Each patch can be applied in order.
@@ -727,9 +727,8 @@ The complete series produces the same end result as your own (probably much messier!) development process did.

We will introduce some tools that can help you do this, explain how to use them, and then explain some of the problems that can arise because -you are rewriting history.

Keeping a patch series up to date using git-rebase

Suppose you have a series of commits in a branch "mywork", which -originally branched off from "origin".

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

$ git checkout -b mywork origin
+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
@@ -751,7 +750,7 @@ 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

Reordering or selecting from a patch series

Given one existing commit, the git-cherry-pick(1) command +return mywork to the state it had before you started the rebase:

$ git rebase --abort

Reordering or selecting from a patch series

Given one existing commit, the 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
@@ -761,9 +760,9 @@ cherry-pick, and possibly modifying them as you go using commit —amend.

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

$ git format-patch origin
$ git reset --hard origin

Then modify, reorder, or eliminate patches as preferred before applying -them again with git-am(1).

Other tools

There are numerous other tools, such as stgit, which exist for the -purpose of maintaining a patch series. These are out of the scope of -this manual.

Problems with rewriting history

The primary problem with rewriting the history of a branch has to do +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 with merging. Suppose somebody fetches your branch and merges it into their branch, with a result something like this:

o--o--O--o--o--o <-- origin
        \                 t--t--t--m <-- their branch:

Then suppose you modify the last three commits:

        o--o--o <-- new head of origin
@@ -782,7 +781,7 @@ 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 7. Advanced branch management

Table of Contents

Fetching individual branches
Understanding git history: 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.

Chapter 7. Advanced branch management

Table of Contents

Fetching individual branches
Understanding git history: 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 repository you originally cloned from. The second argument tells git @@ -804,11 +803,11 @@ resulting in a situation like:

o--o--o--o--a--b &l described in the following section. However, note that in the situation above this may mean losing the commits labeled "a" and "b", unless you've already created a reference of your own pointing to -them.

Forcing git fetch to do non-fast-forward updates

If git fetch fails because the new head of a branch is not a -descendant of the old head, you may force the update with:

$ git fetch git://example.com/proj.git +master:refs/remotes/example/master

Note the addition of the "+" sign. Be aware that commits which the +them.

Forcing git fetch to do non-fast-forward updates

If git fetch fails because the new head of a branch is not a +descendant of the old head, you may force the update with:

$ git fetch git://example.com/proj.git +master:refs/remotes/example/master

Note the addition of the "+" sign. Be aware that commits 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 which you originally cloned from. This information is +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
core.repositoryformatversion=0
@@ -827,8 +826,8 @@ $ 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 8. Git internals

Table of Contents

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

There are two object abstractions: the "object database", and the -"current directory cache" aka "index".

The Object Database

The object database is literally just a content-addressable collection +options mentioned above.

Chapter 8. Git internals

Table of Contents

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