-Git User's Manual (for version 1.5.1 or newer)
+Git User's Manual (for version 1.5.3 or newer)
______________________________________________
-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.
+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.
-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.
+<<repositories-and-branches>> and <<exploring-git-history>> explain how
+to fetch and study a project using git--read these chapters to learn how
+to build and test a particular version of a software project, 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.
+People needing to do actual development will also want to read
+<<Developing-with-git>> and <<sharing-development>>.
Further chapters cover more specialized topics.
$ man git-clone
------------------------------------------------
-Git Quick Start
-===============
-
-This is a quick summary of the major commands; the following chapters
-will explain how these work in more detail.
-
-Creating a new repository
--------------------------
-
-From a tarball:
-
------------------------------------------------
-$ tar xzf project.tar.gz
-$ cd project
-$ git init
-Initialized empty Git repository in .git/
-$ git add .
-$ git commit
------------------------------------------------
-
-From a remote repository:
-
------------------------------------------------
-$ git clone git://example.com/pub/project.git
-$ cd project
------------------------------------------------
-
-Managing branches
------------------
-
------------------------------------------------
-$ git branch # list all branches in this repo
-$ git checkout test # switch working directory to branch "test"
-$ git branch new # create branch "new" starting at current HEAD
-$ git branch -d new # delete branch "new"
------------------------------------------------
-
-Instead of basing new branch on current HEAD (the default), use:
-
------------------------------------------------
-$ git branch new test # branch named "test"
-$ git branch new v2.6.15 # tag named v2.6.15
-$ git branch new HEAD^ # commit before the most recent
-$ git branch new HEAD^^ # commit before that
-$ git branch new test~10 # ten commits before tip of branch "test"
------------------------------------------------
-
-Create and switch to a new branch at the same time:
-
------------------------------------------------
-$ git checkout -b new v2.6.15
------------------------------------------------
-
-Update and examine branches from the repository you cloned from:
-
------------------------------------------------
-$ git fetch # update
-$ git branch -r # list
- origin/master
- origin/next
- ...
-$ git checkout -b masterwork origin/master
------------------------------------------------
-
-Fetch a branch from a different repository, and give it a new
-name in your repository:
-
------------------------------------------------
-$ git fetch git://example.com/project.git theirbranch:mybranch
-$ git fetch git://example.com/project.git v2.6.15:mybranch
------------------------------------------------
-
-Keep a list of repositories you work with regularly:
-
------------------------------------------------
-$ git remote add example git://example.com/project.git
-$ git remote # list remote repositories
-example
-origin
-$ git remote show example # get details
-* remote example
- URL: git://example.com/project.git
- Tracked remote branches
- master next ...
-$ git fetch example # update branches from example
-$ git branch -r # list all remote branches
------------------------------------------------
-
-
-Exploring history
------------------
-
------------------------------------------------
-$ gitk # visualize and browse history
-$ git log # list all commits
-$ git log src/ # ...modifying src/
-$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
-$ git log master..test # ...in branch test, not in branch master
-$ git log test..master # ...in branch master, but not in test
-$ git log test...master # ...in one branch, not in both
-$ git log -S'foo()' # ...where difference contain "foo()"
-$ git log --since="2 weeks ago"
-$ git log -p # show patches as well
-$ git show # most recent commit
-$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
-$ git diff v2.6.15..HEAD # diff with current head
-$ git grep "foo()" # search working directory for "foo()"
-$ git grep v2.6.15 "foo()" # search old tree for "foo()"
-$ git show v2.6.15:a.txt # look at old version of a.txt
------------------------------------------------
-
-Search for regressions:
-
------------------------------------------------
-$ git bisect start
-$ git bisect bad # current version is bad
-$ git bisect good v2.6.13-rc2 # last known good revision
-Bisecting: 675 revisions left to test after this
- # test here, then:
-$ git bisect good # if this revision is good, or
-$ git bisect bad # if this revision is bad.
- # repeat until done.
------------------------------------------------
-
-Making changes
---------------
-
-Make sure git knows who to blame:
-
-------------------------------------------------
-$ cat >~/.gitconfig <<\EOF
-[user]
- name = Your Name Comes Here
- email = you@yourdomain.example.com
-EOF
-------------------------------------------------
-
-Select file contents to include in the next commit, then make the
-commit:
-
------------------------------------------------
-$ git add a.txt # updated file
-$ git add b.txt # new file
-$ git rm c.txt # old file
-$ git commit
------------------------------------------------
-
-Or, prepare and create the commit in one step:
-
------------------------------------------------
-$ git commit d.txt # use latest content only of d.txt
-$ git commit -a # use latest content of all tracked files
------------------------------------------------
-
-Merging
--------
-
------------------------------------------------
-$ git merge test # merge branch "test" into the current branch
-$ git pull git://example.com/project.git master
- # fetch and merge in remote branch
-$ git pull . test # equivalent to git merge test
------------------------------------------------
-
-Sharing your changes
---------------------
-
-Importing or exporting patches:
-
------------------------------------------------
-$ git format-patch origin..HEAD # format a patch for each commit
- # in HEAD but not in origin
-$ git am mbox # import patches from the mailbox "mbox"
------------------------------------------------
-
-Fetch a branch in a different git repository, then merge into the
-current branch:
-
------------------------------------------------
-$ git pull git://example.com/project.git theirbranch
------------------------------------------------
-
-Store the fetched branch into a local branch before merging into the
-current branch:
-
------------------------------------------------
-$ git pull git://example.com/project.git theirbranch:mybranch
------------------------------------------------
-
-After creating commits on a local branch, update the remote
-branch with your commits:
-
------------------------------------------------
-$ git push ssh://example.com/project.git mybranch:theirbranch
------------------------------------------------
-
-When remote and local branch are both named "test":
-
------------------------------------------------
-$ git push ssh://example.com/project.git test
------------------------------------------------
-
-Shortcut version for a frequently used remote repository:
-
------------------------------------------------
-$ git remote add example ssh://example.com/project.git
-$ git push example test
------------------------------------------------
-
-Repository maintenance
-----------------------
-
-Check for corruption:
-
------------------------------------------------
-$ git fsck
------------------------------------------------
+See also <<git-quick-start>> for a brief overview of git commands,
+without any explanation.
-Recompress, remove unused cruft:
+Finally, see <<todo>> for ways that you can help make this manual more
+complete.
------------------------------------------------
-$ git gc
------------------------------------------------
+[[repositories-and-branches]]
Repositories and Branches
=========================
+[[how-to-get-a-git-repository]]
How to get a git repository
---------------------------
It will be useful to have a git repository to experiment with as you
read this manual.
-The best way to get one is by using the gitlink:git-clone[1] command
-to download a copy of an existing repository for a project that you
-are interested in. If you don't already have a project in mind, here
-are some interesting examples:
+The best way to get one is by using the gitlink:git-clone[1] command to
+download a copy of an existing repository. If you don't already have a
+project in mind, here are some interesting examples:
------------------------------------------------
# git itself (approx. 10MB download):
together with a special top-level directory named ".git", which
contains all the information about the history of the project.
-In most of the following, examples will be taken from one of the two
-repositories above.
-
+[[how-to-check-out]]
How to check out a different version of a project
-------------------------------------------------
-Git is best thought of as a tool for storing the history of a
-collection of files. It stores the history as a compressed
-collection of interrelated snapshots (versions) of the project's
-contents.
+Git is best thought of as a tool for storing the history of a collection
+of files. It stores the history as a compressed collection of
+interrelated snapshots of the project's contents. In git each such
+version is called a <<def_commit,commit>>.
A single git repository may contain multiple branches. It keeps track
of them by keeping a list of <<def_head,heads>> which reference the
-latest version on each branch; the gitlink:git-branch[1] command shows
+latest commit on each branch; the gitlink:git-branch[1] command shows
you the list of branch heads:
------------------------------------------------
with no way to find the history it used to point to; so use this command
carefully.
+[[understanding-commits]]
Understanding History: Commits
------------------------------
------------------------------------------------
$ git show
-commit 2b5f6dcce5bf94b9b119e9ed8d537098ec61c3d2
-Author: Jamal Hadi Salim <hadi@cyberus.ca>
-Date: Sat Dec 2 22:22:25 2006 -0800
-
- [XFRM]: Fix aevent structuring to be more complete.
-
- aevents can not uniquely identify an SA. We break the ABI with this
- patch, but consensus is that since it is not yet utilized by any
- (known) application then it is fine (better do it now than later).
-
- Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
- Signed-off-by: David S. Miller <davem@davemloft.net>
-
-diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt
-index 8be626f..d7aac9d 100644
---- a/Documentation/networking/xfrm_sync.txt
-+++ b/Documentation/networking/xfrm_sync.txt
-@@ -47,10 +47,13 @@ aevent_id structure looks like:
+commit 17cf781661e6d38f737f15f53ab552f1e95960d7
+Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
+Date: Tue Apr 19 14:11:06 2005 -0700
+
+ Remove duplicate getenv(DB_ENVIRONMENT) call
+
+ Noted by Tony Luck.
+
+diff --git a/init-db.c b/init-db.c
+index 65898fa..b002dc6 100644
+--- a/init-db.c
++++ b/init-db.c
+@@ -7,7 +7,7 @@
- struct xfrm_aevent_id {
- struct xfrm_usersa_id sa_id;
-+ xfrm_address_t saddr;
- __u32 flags;
-+ __u32 reqid;
- };
-...
+ int main(int argc, char **argv)
+ {
+- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
++ char *sha1_dir, *path;
+ int len, i;
+
+ if (mkdir(".git", 0755) < 0) {
------------------------------------------------
As you can see, a commit shows who made the latest change, what they
contents of the commit, you are guaranteed that the commit can never change
without its name also changing.
-In fact, in <<git-internals>> we shall see that everything stored in git
+In fact, in <<git-concepts>> 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-reachability]]
Understanding history: commits, parents, and reachability
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In the following, we say that commit X is "reachable" from commit Y
if commit X is an ancestor of commit Y. Equivalently, you could say
-that Y is a descendent of X, or that there is a chain of parents
+that Y is a descendant of X, or that there is a chain of parents
leading from commit Y to commit X.
+[[history-diagrams]]
Understanding history: History diagrams
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If we need to talk about a particular commit, the character "o" may
be replaced with another letter or number.
+[[what-is-a-branch]]
Understanding history: What is a branch?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
However, when no confusion will result, we often just use the term
"branch" both for branches and for branch heads.
+[[manipulating-branches]]
Manipulating branches
---------------------
including using a branch name or a tag name
git branch -d <branch>::
delete the branch <branch>; if the branch you are deleting
- points to a commit which is not reachable from this branch,
- this command will fail with a warning.
+ points to a commit which is not reachable from the current
+ branch, this command will fail with a warning.
git branch -D <branch>::
even if the branch points to a commit not reachable
from the current branch, you may know that that commit
------------------------------------------------
$ cat .git/HEAD
427abfa28afedffadfca9dd8b067eb6d36bac53f
-git branch
+$ git branch
* (no branch)
master
------------------------------------------------
In this case we say that the HEAD is "detached".
-This can be an easy way to check out a particular version without having
-to make up a name for a new branch. However, keep in mind that when you
-switch away from the (for example, by checking out something else), you
-can lose track of what the HEAD used to point to.
+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-remote-branches]]
Examining branches from a remote repository
-------------------------------------------
The full name is occasionally useful if, for example, there ever
exists a tag and a branch with the same name.
-As another useful shortcut, if the repository "origin" posesses only
-a single branch, you can refer to that branch as just "origin".
-
-More generally, if you have defined a remote repository named
-"example", you can refer to the branch in that repository as
-"example". And for a repository with multiple branches, this will
-refer to the branch designated as the "HEAD" branch.
+As another useful shortcut, the "HEAD" of a repository can be referred
+to just using the name of that repository. So, for example, "origin"
+is usually a shortcut for the HEAD branch in the repository "origin".
For the complete list of paths which git checks for references, and
the order it uses to decide which to choose when there are multiple
repository. It will not touch any of your own branches--not even the
"master" branch that was created for you on clone.
+[[fetching-branches]]
Fetching branches from other repositories
-----------------------------------------
text editor. (See the "CONFIGURATION FILE" section of
gitlink:git-config[1] for details.)
+[[exploring-git-history]]
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
We start with one specialized tool that is useful for finding the
commit that introduced a bug into a project.
+[[using-bisect]]
How to use bisect to find a regression
--------------------------------------
then test, run "bisect good" or "bisect bad" as appropriate, and
continue.
+[[naming-commits]]
Naming commits
--------------
e05db0fd4f31dde7005f075a84f96b360d05984b
-------------------------------------------------
+[[creating-tags]]
Creating tags
-------------
You can use stable-1 to refer to the commit 1b2e1d63ff.
-This creates a "lightweight" tag. If the tag is a tag you wish to
-share with others, and possibly sign cryptographically, then you
-should create a tag object instead; see the gitlink:git-tag[1] man
-page for details.
+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 gitlink:git-tag[1] man page
+for details.
+[[browsing-revisions]]
Browsing revisions
------------------
multiple independent lines of development, the particular order that
commits are listed in may be somewhat arbitrary.
+[[generating-diffs]]
Generating diffs
----------------
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]]
Viewing old file versions
-------------------------
Before the colon may be anything that names a commit, and after it
may be any path to a file tracked by git.
+[[history-examples]]
Examples
--------
+[[counting-commits-on-a-branch]]
+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
+lower-level command gitlink:git-rev-list[1], which just lists the SHA1's
+of all the given commits:
+
+-------------------------------------------------
+$ git rev-list origin..mybranch | wc -l
+-------------------------------------------------
+
+[[checking-for-equal-branches]]
Check whether two branches point at the same history
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
will return no commits when the two branches are equal.
+[[finding-tagged-descendants]]
Find first tagged version including a given fix
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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-branch]]
+Showing commits unique to a given branch
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Developing with git
-===================
+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.
-Telling git your name
----------------------
+We can list all the heads in this repository with
+gitlink:git-show-ref[1]:
-Before creating any commits, you should introduce yourself to git. The
-easiest way to do so is:
+-------------------------------------------------
+$ 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
+-------------------------------------------------
-------------------------------------------------
-$ cat >~/.gitconfig <<\EOF
-[user]
- name = Your Name Comes Here
- email = you@yourdomain.example.com
-EOF
-------------------------------------------------
+We can get just the branch-head names, and remove "master", with
+the help of the standard utilities cut and grep:
-(See the "CONFIGURATION FILE" section of gitlink:git-config[1] for
-details on the configuration file.)
+-------------------------------------------------
+$ git show-ref --heads | cut -d' ' -f2 | grep -v '^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:
-Creating a new repository
--------------------------
+-------------------------------------------------
+$ 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 $( git show-ref --tags )
+-------------------------------------------------
+
+(See gitlink:git-rev-parse[1] for explanations of commit-selecting
+syntax such as `--not`.)
+
+[[making-a-release]]
+Creating a changelog and tarball for a software release
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The gitlink:git-archive[1] command can create a tar or zip archive from
+any version of a project; for example:
+
+-------------------------------------------------
+$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz
+-------------------------------------------------
+
+will use HEAD to produce a tar archive in which each filename is
+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
+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
+they look OK.
+
+[[Finding-comments-with-given-content]]
+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 --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)
+student. The gitlink:git-log[1], gitlink:git-diff-tree[1], and
+gitlink:git-hash-object[1] man pages may prove helpful.
+
+[[Developing-with-git]]
+Developing with git
+===================
+
+[[telling-git-your-name]]
+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 gitlink:git-config[1] for
+details on the configuration file.)
+
+
+[[creating-a-new-repository]]
+Creating a new repository
+-------------------------
Creating a new repository from scratch is very easy:
-------------------------------------------------
As a special shortcut,
-
+
-------------------------------------------------
$ git commit -a
-------------------------------------------------
-------------------------------------------------
$ 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.
+$ 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.
-------------------------------------------------
+You can also use gitlink:git-gui[1] to create commits, view changes in
+the index and the working tree files, and individually select diff hunks
+for inclusion in the index (by right-clicking on the diff hunk and
+choosing "Stage Hunk For Commit").
+
+[[creating-good-commit-messages]]
Creating good commit messages
-----------------------------
the first line on the Subject line and the rest of the commit in the
body.
+[[ignoring-files]]
+Ignoring files
+--------------
+
+A project will often generate files that you do 'not' want to track with git.
+This typically includes files generated by a build process or temporary
+backup files made by your editor. Of course, 'not' tracking files with git
+is just a matter of 'not' calling "`git add`" on them. But it quickly becomes
+annoying to have these untracked files lying around; e.g. they make
+"`git add .`" and "`git commit -a`" practically useless, and they keep
+showing up in the output of "`git status`".
+
+You can tell git to ignore certain files by creating a file called .gitignore
+in the top level of your working directory, with contents such as:
+
+-------------------------------------------------
+# Lines starting with '#' are considered comments.
+# Ignore any file named foo.txt.
+foo.txt
+# Ignore (generated) html files,
+*.html
+# except foo.html which is maintained by hand.
+!foo.html
+# Ignore objects and archives.
+*.[oa]
+-------------------------------------------------
+
+See gitlink:gitignore[5] for a detailed explanation of the syntax. You can
+also place .gitignore files in other directories in your working tree, and they
+will apply to those directories and their subdirectories. The `.gitignore`
+files can be added to your repository like any other files (just run `git add
+.gitignore` and `git commit`, as usual), which is convenient when the exclude
+patterns (such as patterns matching build output files) would also make sense
+for other users who clone your repository.
+
+If you wish the exclude patterns to affect only certain repositories
+(instead of every repository for a given project), you may instead put
+them in a file in your repository named .git/info/exclude, or in any file
+specified by the `core.excludesfile` configuration variable. Some git
+commands can also take exclude patterns directly on the command line.
+See gitlink:gitignore[5] for the details.
+
+[[how-to-merge]]
How to merge
------------
has two parents, one pointing to the top of the current branch, and
one to the top of the other branch.
-In more detail:
-
[[resolving-a-merge]]
Resolving a merge
-----------------
The above is all you need to know to resolve a simple merge. But git
also provides more information to help resolve conflicts:
+[[conflict-resolution]]
Getting conflict-resolution help during a merge
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
++>>>>>>> 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.
These will display all commits which exist only on HEAD or on
MERGE_HEAD, and which touch an unmerged file.
+You may also use gitlink: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 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
itself have been merged into another branch, as doing so may confuse
further merges.
+[[fast-forwards]]
Fast-forward merges
-------------------
parents, one pointing at each of the two lines of development that
were merged.
-However, if one of the two lines of development is completely
-contained within the other--so every commit present in the one is
-already contained in the other--then git just performs a
-<<fast-forwards,fast forward>>; the head of the current branch is
-moved forward to point at the head of the merged-in branch, without
-any new commits being created.
+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
+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]]
Fixing mistakes
---------------
change, and cannot correctly perform repeated merges from
a branch that has had its history changed.
+[[reverting-a-commit]]
Fixing a mistake with a new commit
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
this is an advanced topic to be left for
<<cleaning-up-history,another chapter>>.
+[[checkout-of-path]]
Checking out an old version of a file
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
which will display the given version of the file.
+[[interrupted-work]]
+Temporarily setting aside work in progress
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+While you are in the middle of working on something complicated, you
+find an unrelated but obvious and trivial bug. You would like to fix it
+before continuing. You can use gitlink:git-stash[1] to save the current
+state of your work, and after fixing the bug (or, optionally after doing
+so on a different branch and then coming back), unstash the
+work-in-progress changes.
+
+------------------------------------------------
+$ git stash "work in progress for foo feature"
+------------------------------------------------
+
+This command will save your changes away to the `stash`, and
+reset your working tree and the index to match the tip of your
+current branch. Then you can make your fix as usual.
+
+------------------------------------------------
+... edit and test ...
+$ git commit -a -m "blorpl: typofix"
+------------------------------------------------
+
+After that, you can go back to what you were working on with
+`git stash apply`:
+
+------------------------------------------------
+$ git stash apply
+------------------------------------------------
+
+
+[[ensuring-good-performance]]
Ensuring good performance
-------------------------
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]]
Ensuring reliability
--------------------
+[[checking-for-corruption]]
Checking the repository for corruption
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...
-------------------------------------------------
-Dangling objects are objects that are harmless, but also unnecessary;
-you can remove them at any time with gitlink:git-prune[1] or the --prune
+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 <<dangling-objects>> for details. However, if
+you wish, you can remove them with gitlink:git-prune[1] or the --prune
option to gitlink:git-gc[1]:
-------------------------------------------------
git-gc when run without any options), it is not safe to prune while
other git operations are in progress in the same repository.
-For more about dangling objects, see <<dangling-objects>>.
-
-
+[[recovering-lost-changes]]
Recovering lost changes
~~~~~~~~~~~~~~~~~~~~~~~
+[[reflogs]]
Reflogs
^^^^^^^
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,
+old history using, for example,
-------------------------------------------------
$ git log master@{1}
$ 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
+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 gitlink:git-reflog[1] and gitlink:git-gc[1] to learn
how to control this pruning, and see the "SPECIFYING REVISIONS"
same project, the reflog history is not shared: it tells you only about
how the branches in your local repository have changed over time.
+[[dangling-object-recovery]]
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 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":
+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
+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
+<<dangling-objects>> for the details.
-------------------------------------------------
$ git fsck
reference pointing to it, for example, a new branch:
------------------------------------------------
-$ git branch recovered-branch 7281251ddd
+$ git branch recovered-branch 7281251ddd
------------------------------------------------
+Other types of dangling objects (blobs and trees) are also possible, and
+dangling objects can arise in other situations.
+
+[[sharing-development]]
Sharing development with others
===============================
$ git pull origin master
-------------------------------------------------
-In fact, "origin" is normally the default repository to pull from,
-and the default branch is normally the HEAD of the remote repository,
-so often you can accomplish the above with just
+In fact, if you have "master" checked out, then by default "git pull"
+merges from the HEAD branch of the origin repository. So often you can
+accomplish the above with just a simple
-------------------------------------------------
$ git pull
-------------------------------------------------
-See the descriptions of the branch.<name>.remote and
-branch.<name>.merge options in gitlink:git-config[1] to learn
-how to control these defaults depending on the current branch.
+More generally, a branch that is created from a remote branch will pull
+by default from that branch. See the descriptions of the
+branch.<name>.remote and branch.<name>.merge options in
+gitlink:git-config[1], and the discussion of the --track option in
+gitlink:git-checkout[1], to learn how to control these defaults.
In addition to saving you keystrokes, "git pull" also helps you by
producing a default commit message documenting the branch and
are roughly equivalent. The former is actually very commonly used.
+[[submitting-patches]]
Submitting patches to a project
-------------------------------
Consult the mailing list for your project first to determine how they
prefer such patches be handled.
+[[importing-patches]]
Importing patches to a project
------------------------------
the original mailbox, with authorship and commit log message each
taken from the message containing each patch.
-[[setting-up-a-public-repository]]
-Setting up a public repository
-------------------------------
+[[public-repositories]]
+Public git repositories
+-----------------------
-Another way to submit changes to a project is to simply tell the
-maintainer of that project to pull from your repository, exactly as
-you did in the section "<<getting-updates-with-git-pull, Getting
-updates with git pull>>".
+Another way to submit changes to a project is to tell the maintainer
+of that project to pull the changes from your repository using
+gitlink:git-pull[1]. In the section "<<getting-updates-with-git-pull,
+Getting updates with git pull>>" we described this as a way to get
+updates from the "main" repository, but it works just as well in the
+other direction.
-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 commands (gitlink:git-clone[1],
-git-fetch[1], git-pull[1], etc.) that accept a URL as an argument
-will also accept a local directory name; so, for example, you can
-use
+If you and the maintainer both have accounts on the same machine, then
+you can just pull changes from each other's repositories directly;
+commands that accept repository URLs as arguments will also accept a
+local directory name:
-------------------------------------------------
$ git clone /path/to/repository
$ git pull /path/to/other/repository
-------------------------------------------------
-If this sort of setup is inconvenient or impossible, another (more
-common) option is to set up a public repository on a public server.
-This also allows you to cleanly separate private work in progress
-from publicly visible work.
+or an ssh url:
+
+-------------------------------------------------
+$ git clone 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
+separate private work in progress from publicly visible work.
You will continue to do your day-to-day work in your personal
repository, but periodically "push" changes from your personal
you push
your personal repo ------------------> your public repo
- ^ |
+ ^ |
| |
| you pull | they pull
| |
| they push V
their public repo <------------------- their repo
-Now, assume your personal repository is in the directory ~/proj. We
-first create a new clone of the repository:
+We explain how to do this in the following sections.
+
+[[setting-up-a-public-repository]]
+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-clone.git
+$ git clone --bare ~/proj proj.git
+$ touch proj.git/git-daemon-export-ok
-------------------------------------------------
-The resulting directory proj-clone.git will contains a "bare" git
-repository--it is just the contents of the ".git" directory, without
-a checked-out copy of a working directory.
+The resulting directory proj.git contains a "bare" git repository--it is
+just the contents of the ".git" directory, without any files checked out
+around it.
-Next, copy proj-clone.git to the server where you plan to host the
+Next, copy proj.git to the server where you plan to host the
public repository. You can use scp, rsync, or whatever is most
convenient.
-If somebody else maintains the public server, they may already have
-set up a git service for you, and you may skip to the section
+[[exporting-via-git]]
+Exporting a git repository via the git protocol
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This is the preferred method.
+
+If someone else administers the server, they should tell you what
+directory to put the repository in, and what git:// url it will appear
+at. You can then skip to the section
"<<pushing-changes-to-a-public-repository,Pushing changes to a public
repository>>", below.
-Otherwise, the following sections explain how to export your newly
-created public repository:
+Otherwise, all you need to do is start gitlink:git-daemon[1]; it will
+listen on port 9418. By default, it will allow access to any directory
+that looks like a git directory and contains the magic file
+git-daemon-export-ok. Passing some directory paths as git-daemon
+arguments will further restrict the exports to those paths.
+
+You can also run git-daemon as an inetd service; see the
+gitlink:git-daemon[1] man page for details. (See especially the
+examples section.)
[[exporting-via-http]]
Exporting a git repository via http
------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The git protocol gives better performance and reliability, but on a
host with a web server set up, http exports may be simpler to set up.
-------------------------------------------------
$ mv proj.git /home/you/public_html/proj.git
$ cd proj.git
-$ git update-server-info
+$ git --bare update-server-info
$ chmod a+x hooks/post-update
-------------------------------------------------
(For an explanation of the last two lines, see
gitlink:git-update-server-info[1], and the documentation
-link:hooks.txt[Hooks used by git].)
+link:hooks.html[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:
+clone or pull from that url, for example with a command line like:
-------------------------------------------------
$ git clone http://yourserver.com/~you/proj.git
for a slightly more sophisticated setup using WebDAV which also
allows pushing over http.)
-[[exporting-via-git]]
-Exporting a git repository via the git protocol
------------------------------------------------
-
-This is the preferred method.
-
-For now, we refer you to the gitlink:git-daemon[1] man page for
-instructions. (See especially the examples section.)
-
[[pushing-changes-to-a-public-repository]]
Pushing changes to a public repository
---------------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Note that the two techniques outline above (exporting via
+Note that the two techniques outlined above (exporting via
<<exporting-via-http,http>> or <<exporting-via-git,git>>) allow other
maintainers to fetch your latest changes, but they do not allow write
access, which you will need to update the public repository with the
$ git push ssh://yourserver.com/~you/proj.git +master
-------------------------------------------------
+Note that the target of a "push" is normally a
+<<def_bare_repository,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
+$ cat >>.git/config <<EOF
[remote "public-repo"]
url = ssh://yourserver.com/~you/proj.git
EOF
and remote.<name>.push options in gitlink:git-config[1] for
details.
+[[setting-up-a-shared-repository]]
Setting up a shared repository
-------------------------------
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Another way to collaborate is by using a model similar to that
commonly used in CVS, where several developers with special rights
all push to and pull from a single shared repository. See
-link:cvs-migration.txt[git for CVS users] for instructions on how to
+link:cvs-migration.html[git for CVS users] for instructions on how to
set this up.
-Allow web browsing of a repository
-----------------------------------
+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
+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
+ high rates. And when that becomes too much, git-pull provides
+ an easy way for that maintainer to delegate this job to other
+ maintainers while still allowing optional review of incoming
+ changes.
+ - Since every developer's repository has the same complete copy
+ of the project history, no repository is special, and it is
+ trivial for another developer to take over maintenance of a
+ project, either by mutual agreement, or because a maintainer
+ becomes unresponsive or difficult to work with.
+ - The lack of a central group of "committers" means there is
+ less need for formal decisions about who is "in" and who is
+ "out".
+
+[[setting-up-gitweb]]
+Allowing 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/INSTALL in the git source tree for instructions on setting it up.
+[[sharing-development-examples]]
Examples
--------
-TODO: topic branches, typical roles as in everyday.txt, ?
+[[maintaining-topic-branches]]
+Maintaining topic branches for a Linux subsystem maintainer
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This describes how Tony Luck uses git in his role as maintainer of the
+IA64 architecture for the Linux kernel.
+
+He uses two public branches:
+
+ - A "test" tree into which patches are initially placed so that they
+ can get some exposure when integrated with other ongoing development.
+ This tree is available to Andrew for pulling into -mm whenever he
+ wants.
+
+ - A "release" tree into which tested patches are moved for final sanity
+ checking, and as a vehicle to send them upstream to Linus (by sending
+ 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,
+and can be updated using gitlink:git-fetch[1]; you can track other
+public trees using gitlink:git-remote[1] to set up a "remote" and
+gitlink:git-fetch[1] to keep them up-to-date; see
+<<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 gitlink: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 gitlink: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
+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
+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 gitlink:git-config[1]) can
+make it easy to push both branches to your public tree. (See
+<<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
+EOF
+-------------------------------------------------
+
+Then you can push both the test and release trees using
+gitlink:git-push[1]:
+
+-------------------------------------------------
+$ git push mytree
+-------------------------------------------------
+
+or push just one of the test and release branches using:
+
+-------------------------------------------------
+$ git push mytree test
+-------------------------------------------------
+
+or
+
+-------------------------------------------------
+$ git push mytree 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
+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
+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
+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
+-------------------------------------------------
+
+or
+
+-------------------------------------------------
+$ git log 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
+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
+
+case "$1" in
+test|release)
+ git checkout $1 && git pull . origin
+ ;;
+origin)
+ before=$(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
+ ;;
+*)
+ echo "Usage: $0 origin|test|release" 1>&2
+ exit 1
+ ;;
+esac
+-------------------------------------------------
+
+-------------------------------------------------
+==== merge script ====
+# Merge a branch into either the test or release branch
+
+pname=$0
+
+usage()
+{
+ echo "Usage: $pname branch test|release" 1>&2
+ exit 1
+}
+
+if [ ! -f .git/refs/heads/"$1" ]
+then
+ echo "Can't see branch <$1>" 1>&2
+ usage
+fi
+
+case "$2" 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 . $1
+ ;;
+*)
+ usage
+ ;;
+esac
+-------------------------------------------------
+
+-------------------------------------------------
+==== status script ====
+# report on status of my ia64 GIT tree
+
+gb=$(tput setab 2)
+rb=$(tput setab 1)
+restore=$(tput setab 9)
+
+if [ `git rev-list test..release | wc -c` -gt 0 ]
+then
+ echo $rb Warning: commits in release that are not in test $restore
+ git log test..release
+fi
+
+for branch in `ls .git/refs/heads`
+do
+ if [ $branch = test -o $branch = release ]
+ then
+ continue
+ 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
+-------------------------------------------------
[[cleaning-up-history]]
However, there is a situation in which it can be useful to violate this
assumption.
+[[patch-series]]
Creating the perfect patch series
---------------------------------
use them, and then explain some of the problems that can arise because
you are rewriting history.
+[[using-git-rebase]]
Keeping a patch series up to date using git-rebase
--------------------------------------------------
\ \
a--b--c--m <-- mywork
................................................
-
+
However, if you prefer to keep the history in mywork a simple series of
commits without any merges, you may instead choose to use
gitlink:git-rebase[1]:
$ git rebase --abort
-------------------------------------------------
+[[modifying-one-commit]]
Modifying a single commit
-------------------------
"modified" existing commits; instead, you have replaced the old commits with
new commits having new object names.
+[[reordering-patch-series]]
Reordering or selecting from a patch series
-------------------------------------------
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.
+cherry-pick, and possibly modifying them as you go using commit --amend.
+The gitlink:git-gui[1] command may also help as it allows you to
+individually select diff hunks for inclusion in the index (by
+right-clicking on the diff hunk and choosing "Stage Hunk for Commit").
Another technique is to use git-format-patch to create a series of
patches, then reset the state to before the patches:
Then modify, reorder, or eliminate patches as preferred before applying
them again with gitlink:git-am[1].
+[[patch-series-tools]]
Other tools
-----------
-There are numerous other tools, such as stgit, which exist for the
+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]]
Problems with rewriting history
-------------------------------
For true distributed development that supports proper merging,
published branches should never be rewritten.
+[[advanced-branch-management]]
Advanced branch management
==========================
+[[fetching-individual-branches]]
Fetching individual branches
----------------------------
will create a new branch named "example-master" and store in it the
branch named "master" from the repository at the given URL. If you
already have a branch named example-master, it will attempt to
-"fast-forward" to the commit given by example.com's master branch. So
-next we explain what a fast-forward is:
+<<fast-forwards,fast-forward>> to the commit given by example.com's
+master branch. In more detail:
-[[fast-forwards]]
-Understanding git history: fast-forwards
-----------------------------------------
+[[fetch-fast-forwards]]
+git fetch and fast-forwards
+---------------------------
In the previous example, when updating an existing branch, "git
fetch" checks to make sure that the most recent commit on the remote
branch is a descendant of the most recent commit on your copy of the
branch before updating your copy of the branch to point at the new
-commit. Git calls this process a "fast forward".
+commit. Git calls this process a <<fast-forwards,fast forward>>.
A fast forward looks something like this:
unless you've already created a reference of your own pointing to
them.
+[[forcing-fetch]]
Forcing git fetch to do non-fast-forward updates
------------------------------------------------
$ 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.
+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
+may be lost, as we saw in the previous section.
+[[remote-branch-configuration]]
Configuring remote branches
---------------------------
then the following commands will all do the same thing:
-------------------------------------------------
-$ git fetch git://example.com/proj.git master:ref/remotes/example/master
-$ git fetch example master:ref/remotes/example/master
-$ git fetch example example/master
+$ git fetch git://example.com/proj.git master:refs/remotes/example/master
+$ git fetch example master:refs/remotes/example/master
$ git fetch example
-------------------------------------------------
options mentioned above.
-[[git-internals]]
-Git internals
-=============
+[[git-concepts]]
+Git concepts
+============
-Git depends on two fundamental abstractions: the "object database", and
-the "current directory cache" aka "index".
+Git is built on a small number of simple but powerful ideas. While it
+is possible to get things done without understanding them, you will find
+git much more intuitive if you do.
+We start with the most important, the <<def_object_database,object
+database>> and the <<def_index,index>>.
+
+[[the-object-database]]
The Object Database
-------------------
-The object database is literally just a content-addressable collection
-of objects. All objects are named by their content, which is
-approximated by the SHA1 hash of the object itself. Objects may refer
-to other objects (by referencing their SHA1 hash), and so you can
-build up a hierarchy of objects.
-
-All objects have a statically determined "type" aka "tag", which is
-determined at object creation time, and which identifies the format of
-the object (i.e. how it is used, and how it can refer to other
-objects). There are currently four different object types: "blob",
-"tree", "commit", and "tag".
-A <<def_blob_object,"blob" object>> cannot refer to any other object,
-and is, as the name implies, a pure storage object containing some
-user data. It is used to actually store the file data, i.e. a blob
-object is associated with some particular version of some file.
-
-A <<def_tree_object,"tree" object>> is an object that ties one or more
-"blob" objects into a directory structure. In addition, a tree object
-can refer to other tree objects, thus creating a directory hierarchy.
-
-A <<def_commit_object,"commit" object>> ties such directory hierarchies
-together into a <<def_DAG,directed acyclic graph>> of revisions - each
-"commit" is associated with exactly one tree (the directory hierarchy at
-the time of the commit). In addition, a "commit" refers to one or more
-"parent" commit objects that describe the history of how we arrived at
-that directory hierarchy.
-
-As a special case, a commit object with no parents is called the "root"
-object, and is the point of an initial project commit. Each project
-must have at least one root, and while you can tie several different
-root objects together into one project by creating a commit object which
-has two or more separate roots as its ultimate parents, that's probably
-just going to confuse people. So aim for the notion of "one root object
-per project", even if git itself does not enforce that.
-
-A <<def_tag_object,"tag" object>> symbolically identifies and can be
-used to sign other objects. It contains the identifier and type of
-another object, a symbolic name (of course!) and, optionally, a
-signature.
+We already saw in <<understanding-commits>> that all commits are stored
+under a 40-digit "object name". In fact, all the information needed to
+represent the history of a project is stored in objects with such names.
+In each case the name is calculated by taking the SHA1 hash of the
+contents of the object. The SHA1 hash is a cryptographic hash function.
+What that means to us is that it is impossible to find two different
+objects with the same name. This has a number of advantages; among
+others:
+
+- Git can quickly determine whether two objects are identical or not,
+ just by comparing names.
+- Since object names are computed the same way in ever repository, the
+ same content stored in two repositories will always be stored under
+ the same name.
+- Git can detect errors when it reads an object, by checking that the
+ object's name is still the SHA1 hash of its contents.
+
+(See <<object-details>> for the details of the object formatting and
+SHA1 calculation.)
+
+There are four different types of objects: "blob", "tree", "commit", and
+"tag".
+
+- A <<def_blob_object,"blob" object>> is used to store file data.
+- A <<def_tree_object,"tree" object>> is an object that ties one or more
+ "blob" objects into a directory structure. In addition, a tree object
+ can refer to other tree objects, thus creating a directory hierarchy.
+- A <<def_commit_object,"commit" object>> ties such directory hierarchies
+ together into a <<def_DAG,directed acyclic graph>> of revisions - each
+ commit contains the object name of exactly one tree designating the
+ directory hierarchy at the time of the commit. In addition, a commit
+ refers to "parent" commit objects that describe the history of how we
+ arrived at that directory hierarchy.
+- A <<def_tag_object,"tag" object>> symbolically identifies and can be
+ used to sign other objects. It contains the object name and type of
+ another object, a symbolic name (of course!) and, optionally, a
+ signature.
-Regardless of object type, all objects share the following
-characteristics: they are all deflated with zlib, and have a header
-that not only specifies their type, but also provides size information
-about the data in the object. It's worth noting that the SHA1 hash
-that is used to name the object is the hash of the original data
-plus this header, so `sha1sum` 'file' does not match the object name
-for 'file'.
-(Historical note: in the dawn of the age of git the hash
-was the sha1 of the 'compressed' object.)
+The object types in some more detail:
-As a result, the general consistency of an object can always be tested
-independently of the contents or the type of the object: all objects can
-be validated by verifying that (a) their hashes match the content of the
-file and (b) the object successfully inflates to a stream of bytes that
-forms a sequence of <ascii type without space> + <space> + <ascii decimal
-size> + <byte\0> + <binary object data>.
+[[commit-object]]
+Commit Object
+~~~~~~~~~~~~~
-The structured objects can further have their structure and
-connectivity to other objects verified. This is generally done with
-the `git-fsck` program, which generates a full dependency graph
-of all objects, and verifies their internal consistency (in addition
-to just verifying their superficial consistency through the hash).
+The "commit" object links a physical state of a tree with a description
+of how we got there and why. Use the --pretty=raw option to
+gitlink:git-show[1] or gitlink:git-log[1] to examine your favorite
+commit:
-The object types in some more detail:
+------------------------------------------------
+$ git show -s --pretty=raw 2be7fcb476
+commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
+tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
+parent 257a84d9d02e90447b149af58b271c19405edb6a
+author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
+committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
-Blob Object
------------
+ Fix misspelling of 'suppress' in docs
-A "blob" object is nothing but a binary blob of data, and doesn't
-refer to anything else. There is no signature or any other
-verification of the data, so while the object is consistent (it 'is'
-indexed by its sha1 hash, so the data itself is certainly correct), it
-has absolutely no other attributes. No name associations, no
-permissions. It is purely a blob of data (i.e. normally "file
-contents").
+ Signed-off-by: Junio C Hamano <gitster@pobox.com>
+------------------------------------------------
-In particular, since the blob is entirely defined by its data, if two
-files in a directory tree (or in multiple different versions of the
-repository) have the same contents, they will share the same blob
-object. The object is totally independent of its location in the
-directory tree, and renaming a file does not change the object that
-file is associated with in any way.
+As you can see, a commit is defined by:
+
+- a tree: The SHA1 name of a tree object (as defined below), representing
+ the contents of a directory at a certain point in time.
+- parent(s): The SHA1 name of some number of commits which represent the
+ immediately prevoius step(s) in the history of the project. The
+ example above has one parent; merge commits may have more than
+ one. A commit with no parents is called a "root" commit, and
+ represents the initial revision of a project. Each project must have
+ at least one root. A project can also have multiple roots, though
+ that isn't common (or necessarily a good idea).
+- an author: The name of the person responsible for this change, together
+ with its date.
+- a committer: The name of the person who actually created the commit,
+ with the date it was done. This may be different from the author, for
+ example, if the author was someone who wrote a patch and emailed it
+ to the person who used it to create the commit.
+- a comment describing this commit.
+
+Note that a commit does not itself contain any information about what
+actually changed; all changes are calculated by comparing the contents
+of the tree referred to by this commit with the trees associated with
+its parents. In particular, git does not attempt to record file renames
+explicitly, though it can identify cases where the existence of the same
+file data at changing paths suggests a rename. (See, for example, the
+-M option to gitlink:git-diff[1]).
+
+A commit is usually created by gitlink:git-commit[1], which creates a
+commit whose parent is normally the current HEAD, and whose tree is
+taken from the content currently stored in the index.
+
+[[tree-object]]
+Tree Object
+~~~~~~~~~~~
-A blob is typically created when gitlink:git-update-index[1]
-is run, and its data can be accessed by gitlink:git-cat-file[1].
+The ever-versatile gitlink:git-show[1] command can also be used to
+examine tree objects, but gitlink:git-ls-tree[1] will give you more
+details:
-Tree Object
------------
+------------------------------------------------
+$ git ls-tree fb3a8bdd0ce
+100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
+100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
+100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
+040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
+100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
+100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
+100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
+100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
+...
+------------------------------------------------
-The next hierarchical object type is the "tree" object. A tree object
-is a list of mode/name/blob data, sorted by name. Alternatively, the
-mode data may specify a directory mode, in which case instead of
-naming a blob, that name is associated with another TREE object.
-
-Like the "blob" object, a tree object is uniquely determined by the
-set contents, and so two separate but identical trees will always
-share the exact same object. This is true at all levels, i.e. it's
-true for a "leaf" tree (which does not refer to any other trees, only
-blobs) as well as for a whole subdirectory.
-
-For that reason a "tree" object is just a pure data abstraction: it
-has no history, no signatures, no verification of validity, except
-that since the contents are again protected by the hash itself, we can
-trust that the tree is immutable and its contents never change.
-
-So you can trust the contents of a tree to be valid, the same way you
-can trust the contents of a blob, but you don't know where those
-contents 'came' from.
-
-Side note on trees: since a "tree" object is a sorted list of
-"filename+content", you can create a diff between two trees without
-actually having to unpack two trees. Just ignore all common parts,
-and your diff will look right. In other words, you can effectively
-(and efficiently) tell the difference between any two random trees by
-O(n) where "n" is the size of the difference, rather than the size of
-the tree.
-
-Side note 2 on trees: since the name of a "blob" depends entirely and
-exclusively on its contents (i.e. there are no names or permissions
-involved), you can see trivial renames or permission changes by
-noticing that the blob stayed the same. However, renames with data
-changes need a smarter "diff" implementation.
-
-A tree is created with gitlink:git-write-tree[1] and
-its data can be accessed by gitlink:git-ls-tree[1].
-Two trees can be compared with gitlink:git-diff-tree[1].
+As you can see, a tree object contains a list of entries, each with a
+mode, object type, SHA1 name, and name, sorted by name. It represents
+the contents of a single directory tree.
-Commit Object
--------------
+The object type may be a blob, representing the contents of a file, or
+another tree, representing the contents of a subdirectory. Since trees
+and blobs, like all other objects, are named by the SHA1 hash of their
+contents, two trees have the same SHA1 name if and only if their
+contents (including, recursively, the contents of all subdirectories)
+are identical. This allows git to quickly determine the differences
+between two related tree objects, since it can ignore any entries with
+identical object names.
+
+(Note: in the presence of submodules, trees may also have commits as
+entries. See gitlink:git-submodule[1] and gitlink:gitmodules.txt[1]
+for partial documentation.)
+
+Note that the files all have mode 644 or 755: git actually only pays
+attention to the executable bit.
+
+[[blob-object]]
+Blob Object
+~~~~~~~~~~~
+
+You can use gitlink:git-show[1] to examine the contents of a blob; take,
+for example, the blob in the entry for "COPYING" from the tree above:
+
+------------------------------------------------
+$ git show 6ff87c4664
+
+ Note that the only valid version of the GPL as far as this project
+ is concerned is _this_ particular version of the license (ie v2, not
+ v2.2 or v3.x or whatever), unless explicitly otherwise stated.
+...
+------------------------------------------------
-The "commit" object is an object that introduces the notion of
-history into the picture. In contrast to the other objects, it
-doesn't just describe the physical state of a tree, it describes how
-we got there, and why.
-
-A "commit" is defined by the tree-object that it results in, the
-parent commits (zero, one or more) that led up to that point, and a
-comment on what happened. Again, a commit is not trusted per se:
-the contents are well-defined and "safe" due to the cryptographically
-strong signatures at all levels, but there is no reason to believe
-that the tree is "good" or that the merge information makes sense.
-The parents do not have to actually have any relationship with the
-result, for example.
-
-Note on commits: unlike real SCM's, commits do not contain
-rename information or file mode change information. All of that is
-implicit in the trees involved (the result tree, and the result trees
-of the parents), and describing that makes no sense in this idiotic
-file manager.
-
-A commit is created with gitlink:git-commit-tree[1] and
-its data can be accessed by gitlink:git-cat-file[1].
+A "blob" object is nothing but a binary blob of data. It doesn't refer
+to anything else or have attributes of any kind.
+Since the blob is entirely defined by its data, if two files in a
+directory tree (or in multiple different versions of the repository)
+have the same contents, they will share the same blob object. The object
+is totally independent of its location in the directory tree, and
+renaming a file does not change the object that file is associated with.
+
+Note that any tree or blob object can be examined using
+gitlink:git-show[1] with the <revision>:<path> syntax. This can
+sometimes be useful for browsing the contents of a tree that is not
+currently checked out.
+
+[[trust]]
Trust
------
+~~~~~
-An aside on the notion of "trust". Trust is really outside the scope
-of "git", but it's worth noting a few things. First off, since
-everything is hashed with SHA1, you 'can' trust that an object is
-intact and has not been messed with by external sources. So the name
-of an object uniquely identifies a known state - just not a state that
-you may want to trust.
+If you receive the SHA1 name of a blob from one source, and its contents
+from another (possibly untrusted) source, you can still trust that those
+contents are correct as long as the SHA1 name agrees. This is because
+the SHA1 is designed so that it is infeasible to find different contents
+that produce the same hash.
-Furthermore, since the SHA1 signature of a commit refers to the
-SHA1 signatures of the tree it is associated with and the signatures
-of the parent, a single named commit specifies uniquely a whole set
-of history, with full contents. You can't later fake any step of the
-way once you have the name of a commit.
+Similarly, you need only trust the SHA1 name of a top-level tree object
+to trust the contents of the entire directory that it refers to, and if
+you receive the SHA1 name of a commit from a trusted source, then you
+can easily verify the entire history of commits reachable through
+parents of that commit, and all of those contents of the trees referred
+to by those commits.
So to introduce some real trust in the system, the only thing you need
to do is to digitally sign just 'one' special note, which includes the
To assist in this, git also provides the tag object...
+[[tag-object]]
Tag Object
-----------
+~~~~~~~~~~
-Git provides the "tag" object to simplify creating, managing and
-exchanging symbolic and signed tokens. The "tag" object at its
-simplest simply symbolically identifies another object by containing
-the sha1, type and symbolic name.
+A tag object contains an object, object type, tag name, the name of the
+person ("tagger") who created the tag, and a message, which may contain
+a signature, as can be seen using the gitlink:git-cat-file[1]:
-However it can optionally contain additional signature information
-(which git doesn't care about as long as there's less than 8k of
-it). This can then be verified externally to git.
+------------------------------------------------
+$ git cat-file tag v1.5.0
+object 437b1b20df4b356c9342dac8d38849f24ef44f27
+type commit
+tag v1.5.0
+tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000
+
+GIT 1.5.0
+-----BEGIN PGP SIGNATURE-----
+Version: GnuPG v1.4.6 (GNU/Linux)
+
+iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
+nLE/L9aUXdWeTFPron96DLA=
+=2E+0
+-----END PGP SIGNATURE-----
+------------------------------------------------
-Note that despite the tag features, "git" itself only handles content
-integrity; the trust framework (and signature provision and
-verification) has to come from outside.
+See the gitlink:git-tag[1] command to learn how to create and verify tag
+objects. (Note that gitlink:git-tag[1] can also be used to create
+"lightweight tags", which are not tag objects at all, but just simple
+references in .git/refs/tags/).
-A tag is created with gitlink:git-mktag[1],
-its data can be accessed by gitlink:git-cat-file[1],
-and the signature can be verified by
-gitlink:git-verify-tag[1].
+[[pack-files]]
+How git stores objects efficiently: pack files
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Newly created objects are initially created in a file named after the
+object's SHA1 hash (stored in .git/objects).
-The "index" aka "Current Directory Cache"
------------------------------------------
+Unfortunately this system becomes inefficient once a project has a
+lot of objects. Try this on an old project:
+
+------------------------------------------------
+$ git count-objects
+6930 objects, 47620 kilobytes
+------------------------------------------------
+
+The first number is the number of objects which are kept in
+individual files. The second is the amount of space taken up by
+those "loose" objects.
+
+You can save space and make git faster by moving these loose objects in
+to a "pack file", which stores a group of objects in an efficient
+compressed format; the details of how pack files are formatted can be
+found in link:technical/pack-format.txt[technical/pack-format.txt].
+
+To put the loose objects into a pack, just run git repack:
+
+------------------------------------------------
+$ git repack
+Generating pack...
+Done counting 6020 objects.
+Deltifying 6020 objects.
+ 100% (6020/6020) done
+Writing 6020 objects.
+ 100% (6020/6020) done
+Total 6020, written 6020 (delta 4070), reused 0 (delta 0)
+Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created.
+------------------------------------------------
+
+You can then run
+
+------------------------------------------------
+$ git prune
+------------------------------------------------
+
+to remove any of the "loose" objects that are now contained in the
+pack. This will also remove any unreferenced objects (which may be
+created when, for example, you use "git reset" to remove a commit).
+You can verify that the loose objects are gone by looking at the
+.git/objects directory or by running
+
+------------------------------------------------
+$ git count-objects
+0 objects, 0 kilobytes
+------------------------------------------------
+
+Although the object files are gone, any commands that refer to those
+objects will work exactly as they did before.
+
+The gitlink:git-gc[1] command performs packing, pruning, and more for
+you, so is normally the only high-level command you need.
+
+[[dangling-objects]]
+Dangling objects
+~~~~~~~~~~~~~~~~
+
+The gitlink:git-fsck[1] command will sometimes complain about dangling
+objects. They are not a problem.
+
+The most common cause of dangling objects is that you've rebased a
+branch, or you have pulled from somebody else who rebased a branch--see
+<<cleaning-up-history>>. In that case, the old head of the original
+branch still exists, as does 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
+file, but then, before you actually committed it and made it part of the
+bigger picture, you changed something else in that file and committed
+that *updated* thing - the old state that you added originally ends up
+not being pointed to by any commit or tree, so it's now a dangling blob
+object.
+
+Similarly, when the "recursive" merge strategy runs, and finds that
+there are criss-cross merges and thus more than one merge base (which is
+fairly unusual, but it does happen), it will generate one temporary
+midway tree (or possibly even more, if you had lots of criss-crossing
+merges and more than two merge bases) as a temporary internal merge
+base, and again, those are real objects, but the end result will not end
+up pointing to them, so they end up "dangling" in your repository.
+
+Generally, dangling objects aren't anything to worry about. They can
+even be very useful: if you screw something up, the dangling objects can
+be how you recover your old tree (say, you did a rebase, and realized
+that you really didn't want to - you can look at what dangling objects
+you have, and decide to reset your head to some old dangling state).
+
+For commits, 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
+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
+what the "ls" for that directory was), and that may give you some idea
+of what the operation was that left that dangling object.
+
+Usually, dangling blobs and trees aren't very interesting. They're
+almost always the result of either being a half-way mergebase (the blob
+will often even have the conflict markers from a merge in it, if you
+have had conflicting merges that you fixed up by hand), or simply
+because you interrupted a "git fetch" with ^C or something like that,
+leaving _some_ of the new objects in the object database, but just
+dangling and useless.
+
+Anyway, once you are sure that you're not interested in any dangling
+state, you can just prune all unreachable objects:
+
+------------------------------------------------
+$ git prune
+------------------------------------------------
+
+and they'll be gone. But you should only run "git prune" on a quiescent
+repository - it's kind of like doing a filesystem fsck recovery: you
+don't want to do that while the filesystem is mounted.
+
+(The same is true of "git-fsck" itself, btw - but since
+git-fsck never actually *changes* the repository, it just reports
+on what it found, git-fsck itself is never "dangerous" to run.
+Running it while somebody is actually changing the repository can cause
+confusing and scary messages, but it won't actually do anything bad. In
+contrast, running "git prune" while somebody is actively changing the
+repository is a *BAD* idea).
-The index is a simple binary file, which contains an efficient
-representation of a virtual directory content at some random time. It
-does so by a simple array that associates a set of names, dates,
-permissions and content (aka "blob") objects together. The cache is
-always kept ordered by name, and names are unique (with a few very
-specific rules) at any point in time, but the cache has no long-term
-meaning, and can be partially updated at any time.
-
-In particular, the index certainly does not need to be consistent with
-the current directory contents (in fact, most operations will depend on
-different ways to make the index 'not' be consistent with the directory
-hierarchy), but it has three very important attributes:
-
-'(a) it can re-generate the full state it caches (not just the
-directory structure: it contains pointers to the "blob" objects so
-that it can regenerate the data too)'
-
-As a special case, there is a clear and unambiguous one-way mapping
-from a current directory cache to a "tree object", which can be
-efficiently created from just the current directory cache without
-actually looking at any other data. So a directory cache at any one
-time uniquely specifies one and only one "tree" object (but has
-additional data to make it easy to match up that tree object with what
-has happened in the directory)
-
-'(b) it has efficient methods for finding inconsistencies between that
-cached state ("tree object waiting to be instantiated") and the
-current state.'
-
-'(c) it can additionally efficiently represent information about merge
-conflicts between different tree objects, allowing each pathname to be
+[[the-index]]
+The index
+-----------
+
+The index is a binary file (generally kept in .git/index) containing a
+sorted list of path names, each with permissions and the SHA1 of a blob
+object; gitlink:git-ls-files[1] can show you the contents of the index:
+
+-------------------------------------------------
+$ git ls-files --stage
+100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore
+100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap
+100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING
+100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore
+100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile
+...
+100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h
+100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c
+100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h
+-------------------------------------------------
+
+Note that in older documentation you may see the index called the
+"current directory cache" or just the "cache". It has three important
+properties:
+
+1. The index contains all the information necessary to generate a single
+(uniquely determined) tree object.
++
+For example, running gitlink:git-commit[1] generates this tree object
+from the index, stores it in the object database, and uses it as the
+tree object associated with the new commit.
+
+2. The index enables fast comparisons between the tree object it defines
+and the working tree.
++
+It does this by storing some additional data for each entry (such as
+the last modified time). This data is not displayed above, and is not
+stored in the created tree object, but it can be used to determine
+quickly which files in the working directory differ from what was
+stored in the index, and thus save git from having to read all of the
+data from such files to look for changes.
+
+3. It can efficiently represent information about merge conflicts
+between different tree objects, allowing each pathname to be
associated with sufficient information about the trees involved that
-you can create a three-way merge between them.'
+you can create a three-way merge between them.
++
+We saw in <<conflict-resolution>> that during a merge the index can
+store multiple versions of a single file (called "stages"). The third
+column in the gitlink:git-ls-files[1] output above is the stage
+number, and will take on values other than 0 for files with merge
+conflicts.
+
+The index is thus a sort of temporary staging area, which is filled with
+a tree which you are in the process of working on.
+
+If you blow the index away entirely, you generally haven't lost any
+information as long as you have the name of the tree that it described.
+
+[[low-level-operations]]
+Low-level git operations
+========================
+
+Many of the higher-level commands were originally implemented as shell
+scripts using a smaller core of low-level git commands. These can still
+be useful when doing unusual things with git, or just as a way to
+understand its inner workings.
+
+[[object-manipulation]]
+Object access and manipulation
+------------------------------
-Those are the ONLY three things that the directory cache does. It's a
-cache, and the normal operation is to re-generate it completely from a
-known tree object, or update/compare it with a live tree that is being
-developed. If you blow the directory cache away entirely, you generally
-haven't lost any information as long as you have the name of the tree
-that it described.
+The gitlink:git-cat-file[1] command can show the contents of any object,
+though the higher-level gitlink:git-show[1] is usually more useful.
-At the same time, the index is at the same time also the
-staging area for creating new trees, and creating a new tree always
-involves a controlled modification of the index file. In particular,
-the index file can have the representation of an intermediate tree that
-has not yet been instantiated. So the index can be thought of as a
-write-back cache, which can contain dirty information that has not yet
-been written back to the backing store.
+The gitlink:git-commit-tree[1] command allows constructing commits with
+arbitrary parents and trees.
+A tree can be created with gitlink:git-write-tree[1] and its data can be
+accessed by gitlink:git-ls-tree[1]. Two trees can be compared with
+gitlink:git-diff-tree[1].
+A tag is created with gitlink:git-mktag[1], and the signature can be
+verified by gitlink:git-verify-tag[1], though it is normally simpler to
+use gitlink:git-tag[1] for both.
+[[the-workflow]]
The Workflow
------------
+High-level operations such as gitlink:git-commit[1],
+gitlink:git-checkout[1] and git-reset[1] work by moving data between the
+working tree, the index, and the object database. Git provides
+low-level operations which perform each of these steps individually.
+
Generally, all "git" operations work on the index file. Some operations
work *purely* on the index file (showing the current state of the
-index), but most operations move data to and from the index file. Either
-from the database or from the working directory. Thus there are four
-main combinations:
+index), but most operations move data between the index file and either
+the database or the working directory. Thus there are four main
+combinations:
+[[working-directory-to-index]]
working directory -> index
~~~~~~~~~~~~~~~~~~~~~~~~~~
-You update the index with information from the working directory with
-the gitlink:git-update-index[1] command. You
-generally update the index information by just specifying the filename
-you want to update, like so:
+The gitlink:git-update-index[1] command updates the index with
+information from the working directory. You generally update the
+index information by just specifying the filename you want to update,
+like so:
-------------------------------------------------
-$ git-update-index filename
+$ git update-index filename
-------------------------------------------------
but to avoid common mistakes with filename globbing etc, the command
it will only update the fields that are used to quickly test whether
an object still matches its old backing store object.
+The previously introduced gitlink:git-add[1] is just a wrapper for
+gitlink:git-update-index[1].
+
+[[index-to-object-database]]
index -> object database
~~~~~~~~~~~~~~~~~~~~~~~~
You write your current index file to a "tree" object with the program
-------------------------------------------------
-$ git-write-tree
+$ git write-tree
-------------------------------------------------
that doesn't come with any options - it will just write out the
use that tree to re-generate the index at any time by going in the
other direction:
+[[object-database-to-index]]
object database -> index
~~~~~~~~~~~~~~~~~~~~~~~~
earlier. However, that is only your 'index' file: your working
directory contents have not been modified.
+[[index-to-working-directory]]
index -> working directory
~~~~~~~~~~~~~~~~~~~~~~~~~~
Finally, there are a few odds and ends which are not purely moving
from one representation to the other:
+[[tying-it-all-together]]
Tying it all together
~~~~~~~~~~~~~~~~~~~~~
------------
+[[examining-the-data]]
Examining the data
------------------
to see what the top commit was.
+[[merging-multiple-trees]]
Merging multiple trees
----------------------
object.
Once you know the three trees you are going to merge (the one "original"
-tree, aka the common case, and the two "result" trees, aka the branches
+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
`git-write-tree`.
+[[merging-multiple-trees-2]]
Merging multiple trees, continued
---------------------------------
above example shows is that file `hello.c` was changed from
`$orig` to `HEAD` and `$orig` to `$target` in a different way.
You could resolve this by running your favorite 3-way merge
-program, e.g. `diff3` or `merge`, on the blob objects from
-these three stages yourself, like this:
+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
-$ merge hello.c~2 hello.c~1 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
and that is what higher level `git merge -s resolve` is implemented with.
-How git stores objects efficiently: pack files
-----------------------------------------------
+[[hacking-git]]
+Hacking git
+===========
-We've seen how git stores each object in a file named after the
-object's SHA1 hash.
+This chapter covers internal details of the git implementation which
+probably only git developers need to understand.
-Unfortunately this system becomes inefficient once a project has a
-lot of objects. Try this on an old project:
+[[object-details]]
+Object storage format
+---------------------
-------------------------------------------------
-$ git count-objects
-6930 objects, 47620 kilobytes
-------------------------------------------------
+All objects have a statically determined "type" which identifies the
+format of the object (i.e. how it is used, and how it can refer to other
+objects). There are currently four different object types: "blob",
+"tree", "commit", and "tag".
-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.
+Regardless of object type, all objects share the following
+characteristics: they are all deflated with zlib, and have a header
+that not only specifies their type, but also provides size information
+about the data in the object. It's worth noting that the SHA1 hash
+that is used to name the object is the hash of the original data
+plus this header, so `sha1sum` 'file' does not match the object name
+for 'file'.
+(Historical note: in the dawn of the age of git the hash
+was the sha1 of the 'compressed' object.)
-You can save space and make git faster by moving these loose objects in
-to a "pack file", which stores a group of objects in an efficient
-compressed format; the details of how pack files are formatted can be
-found in link:technical/pack-format.txt[technical/pack-format.txt].
+As a result, the general consistency of an object can always be tested
+independently of the contents or the type of the object: all objects can
+be validated by verifying that (a) their hashes match the content of the
+file and (b) the object successfully inflates to a stream of bytes that
+forms a sequence of <ascii type without space> {plus} <space> {plus} <ascii decimal
+size> {plus} <byte\0> {plus} <binary object data>.
-To put the loose objects into a pack, just run git repack:
+The structured objects can further have their structure and
+connectivity to other objects verified. This is generally done with
+the `git-fsck` program, which generates a full dependency graph
+of all objects, and verifies their internal consistency (in addition
+to just verifying their superficial consistency through the hash).
-------------------------------------------------
-$ 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.
-------------------------------------------------
+[[birdview-on-the-source-code]]
+A birds-eye view of Git's source code
+-------------------------------------
-You can then run
+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.
-------------------------------------------------
-$ git prune
-------------------------------------------------
+A good place to start is with the contents of the initial commit, with:
-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 checkout e83c5163
+----------------------------------------------------
-------------------------------------------------
-$ git count-objects
-0 objects, 0 kilobytes
-------------------------------------------------
+The initial revision lays the foundation for almost everything git has
+today, but is small enough to read in one sitting.
-Although the object files are gone, any commands that refer to those
-objects will work exactly as they did before.
+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 <<def_commit_object,commit>>.
-The gitlink:git-gc[1] command performs packing, pruning, and more for
-you, so is normally the only high-level command you need.
+Also, we do not call it "cache" any more, but "index", however, the
+file is still called `cache.h`. Remark: Not much reason to change it now,
+especially since there is no good single name for it anyway, because it is
+basically _the_ header file which is included by _all_ of Git's C sources.
-[[dangling-objects]]
-Dangling objects
-----------------
+If you grasp the ideas in that initial commit, you should check out a
+more recent version and skim `cache.h`, `object.h` and `commit.h`.
-The gitlink:git-fsck[1] command will sometimes complain about dangling
-objects. They are not a problem.
+In the early days, Git (in the tradition of UNIX) was a bunch of programs
+which were extremely simple, and which you used in scripts, piping the
+output of one into another. This turned out to be good for initial
+development, since it was easier to test new things. However, recently
+many of these parts have become builtins, and some of the core has been
+"libified", i.e. put into libgit.a for performance, portability reasons,
+and to avoid code duplication.
-The most common cause of dangling objects is that you've rebased a
-branch, or you have pulled from somebody else who rebased a branch--see
-<<cleaning-up-history>>. In that case, the old head of the original
-branch still exists, as does obviously everything it pointed to. The
-branch pointer itself just doesn't, since you replaced it with another
-one.
+By now, you know what the index is (and find the corresponding data
+structures in `cache.h`), and that there are just a couple of object types
+(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).
-There are also other situations too that cause dangling objects. For
-example, a "dangling blob" may arise because you did a "git add" of a
-file, but then, before you actually committed it and made it part of the
-bigger picture, you changed something else in that file and committed
-that *updated* thing - the old state that you added originally ends up
-not being pointed to by any commit or tree, so it's now a dangling blob
-object.
+Now is a good point to take a break to let this information sink in.
-Similarly, when the "recursive" merge strategy runs, and finds that
-there are criss-cross merges and thus more than one merge base (which is
-fairly unusual, but it does happen), it will generate one temporary
-midway tree (or possibly even more, if you had lots of criss-crossing
-merges and more than two merge bases) as a temporary internal merge
-base, and again, those are real objects, but the end result will not end
-up pointing to them, so they end up "dangling" in your repository.
+Next step: get familiar with the object naming. Read <<naming-commits>>.
+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.
-Generally, dangling objects aren't anything to worry about. They can
-even be very useful: if you screw something up, the dangling objects can
-be how you recover your old tree (say, you did a rebase, and realized
-that you really didn't want to - you can look at what dangling objects
-you have, and decide to reset your head to some old dangling state).
+This is just to get you into the groove for the most libified part of Git:
+the revision walker.
-For commits, the most useful thing to do with dangling objects tends to
-be to do a simple
+Basically, the initial version of `git log` was a shell script:
-------------------------------------------------
-$ gitk <dangling-commit-sha-goes-here> --not --all
-------------------------------------------------
+----------------------------------------------------------------
+$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
+ LESS=-S ${PAGER:-less}
+----------------------------------------------------------------
-For blobs and trees, you can't do the same, but you can examine them.
-You can just do
+What does this mean?
-------------------------------------------------
-$ git show <dangling-blob/tree-sha-goes-here>
-------------------------------------------------
+`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`.
-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.
+`git-rev-parse` is not as important any more; it was only used to filter out
+options that were relevant for the different plumbing commands that were
+called by the script.
-Usually, dangling blobs and trees aren't very interesting. They're
-almost always the result of either being a half-way mergebase (the blob
-will often even have the conflict markers from a merge in it, if you
-have had conflicting merges that you fixed up by hand), or simply
-because you interrupted a "git fetch" with ^C or something like that,
-leaving _some_ of the new objects in the object database, but just
-dangling and useless.
+Most of what `git-rev-list` did is contained in `revision.c` and
+`revision.h`. It wraps the options in a struct named `rev_info`, which
+controls how and what revisions are walked, and more.
-Anyway, once you are sure that you're not interested in any dangling
-state, you can just prune all unreachable objects:
+The original job of `git-rev-parse` is now taken by the function
+`setup_revisions()`, which parses the revisions and the common command line
+options for the revision walker. This information is stored in the struct
+`rev_info` for later consumption. You can do your own command line option
+parsing after calling `setup_revisions()`. After that, you have to call
+`prepare_revision_walk()` for initialization, and then you can get the
+commits one by one with the function `get_revision()`.
+
+If you are interested in more details of the revision walking process,
+just have a look at the first implementation of `cmd_log()`; call
+`git-show v1.3.0~155^2~4` and scroll down to that function (note that you
+no longer need to call `setup_pager()` directly).
+
+Nowadays, `git log` is a builtin, which means that it is _contained_ in the
+command `git`. The source side of a builtin is
+
+- a function called `cmd_<bla>`, typically defined in `builtin-<bla>.c`,
+ and declared in `builtin.h`,
+
+- an entry in the `commands[]` array in `git.c`, and
+
+- an entry in `BUILTIN_OBJECTS` in the `Makefile`.
+
+Sometimes, more than one builtin is contained in one source file. For
+example, `cmd_whatchanged()` and `cmd_log()` both reside in `builtin-log.c`,
+since they share quite a bit of code. In that case, the commands which are
+_not_ named like the `.c` file in which they live have to be listed in
+`BUILT_INS` in the `Makefile`.
+
+`git log` looks more complicated in C than it does in the original script,
+but that allows for a much greater flexibility and performance.
+
+Here again it is a good point to take a pause.
+
+Lesson three is: study the code. Really, it is the best way to learn about
+the organization of Git (after you know the basic concepts).
+
+So, think about something which you are interested in, say, "how can I
+access a blob just knowing the object name of it?". The first step is to
+find a Git command with which you can do it. In this example, it is either
+`git show` or `git cat-file`.
+
+For the sake of clarity, let's stay with `git cat-file`, because it
+
+- is plumbing, and
+
+- 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
+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.
+
+- the variable `sha1` in the function signature of `get_sha1()` is `unsigned
+ char \*`, but is actually expected to be a pointer to `unsigned
+ char[20]`. This variable will contain the 160-bit SHA-1 of the given
+ commit. Note that whenever a SHA-1 is passed as `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
+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,
+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!
+
+[[glossary]]
+include::glossary.txt[]
+
+[[git-quick-start]]
+Appendix A: Git Quick Reference
+===============================
+
+This is a quick summary of the major commands; the previous chapters
+explain how these work in more detail.
+
+[[quick-creating-a-new-repository]]
+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]]
+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
+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]]
+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]]
+Making changes
+--------------
+
+Make sure git knows who to blame:
------------------------------------------------
-$ git prune
+$ cat >>~/.gitconfig <<\EOF
+[user]
+ name = Your Name Comes Here
+ email = you@yourdomain.example.com
+EOF
------------------------------------------------
-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.
+Select file contents to include in the next commit, then make the
+commit:
-(The same is true of "git-fsck" itself, btw - but since
-git-fsck never actually *changes* the repository, it just reports
-on what it found, git-fsck itself is never "dangerous" to run.
-Running it while somebody is actually changing the repository can cause
-confusing and scary messages, but it won't actually do anything bad. In
-contrast, running "git prune" while somebody is actively changing the
-repository is a *BAD* idea).
+-----------------------------------------------
+$ git add a.txt # updated file
+$ git add b.txt # new file
+$ git rm c.txt # old file
+$ git commit
+-----------------------------------------------
-include::glossary.txt[]
+Or, prepare and create the commit in one step:
-Notes and todo list for this manual
-===================================
+-----------------------------------------------
+$ git commit d.txt # use latest content only of d.txt
+$ git commit -a # use latest content of all tracked files
+-----------------------------------------------
+
+[[merging]]
+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]]
+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]]
+Repository maintenance
+----------------------
+
+Check for corruption:
+
+-----------------------------------------------
+$ git fsck
+-----------------------------------------------
+
+Recompress, remove unused cruft:
+
+-----------------------------------------------
+$ git gc
+-----------------------------------------------
+
+
+[[todo]]
+Appendix B: Notes and todo list for this manual
+===============================================
This is a work in progress.
The basic requirements:
- - It must be readable in order, from beginning to end, by
- someone intelligent with a basic grasp of the unix
- commandline, but without any special knowledge of git. If
- necessary, any other prerequisites should be specifically
- mentioned as they arise.
- - Whenever possible, section headings should clearly describe
- the task they explain how to do, in language that requires
- no more knowledge than necessary: for example, "importing
- patches into a project" rather than "the git-am command"
+
+- It must be readable in order, from beginning to end, by someone
+ intelligent with a basic grasp of the UNIX command line, but without
+ any special knowledge of git. If necessary, any other prerequisites
+ should be specifically mentioned as they arise.
+- Whenever possible, section headings should clearly describe the task
+ they explain how to do, in language that requires no more knowledge
+ than necessary: for example, "importing patches into a project" rather
+ than "the git-am command"
Think about how to create a clear chapter dependency graph that will
allow people to get to important topics without necessarily reading
everything in between.
-Say something about .gitignore.
-
Scan Documentation/ for other stuff left out; in particular:
- howto's
- some of technical/?
- hooks
- list of commands in gitlink:git[1]
+
+- howto's
+- some of technical/?
+- hooks
+- list of commands in gitlink:git[1]
Scan email archives for other stuff left out
More details on gitweb?
Write a chapter on using plumbing and writing scripts.
+
+Alternates, clone -reference, etc.
+
+git unpack-objects -r for recovery
+
+submodules