Git User Manual
-_______________
+===============
Git is a fast distributed revision control system.
a summary of the commands:
`git branch`::
- list all branches
+ list all branches.
`git branch <branch>`::
create a new branch named `<branch>`, referencing the same
- point in history as the current branch
+ point in history as the current branch.
`git branch <branch> <start-point>`::
create a new branch named `<branch>`, referencing
`<start-point>`, which may be specified any way you like,
- including using a branch name or a tag name
+ 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 the current
- branch, this command will fail with a warning.
+ delete the branch `<branch>`; if the branch is not fully
+ merged in its upstream branch or contained in 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
- is still reachable from some other branch or tag. In that
- case it is safe to use this command to force Git to delete
- the branch.
+ delete the branch `<branch>` irrespective of its merged status.
`git checkout <branch>`::
make the current branch `<branch>`, updating the working
- directory to reflect the version referenced by `<branch>`
+ directory to reflect the version referenced by `<branch>`.
`git checkout -b <new> <start-point>`::
create a new branch `<new>` referencing `<start-point>`, and
check it out.
-------------------------------------------------
(See also
-link:howto/setup-git-server-over-http.txt[setup-git-server-over-http]
+link:howto/setup-git-server-over-http.html[setup-git-server-over-http]
for a slightly more sophisticated setup using WebDAV which also
allows pushing over HTTP.)
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].
+found in link:technical/pack-format.html[pack format].
To put the loose objects into a pack, just run git repack:
$ git prune
------------------------------------------------
-and they'll be gone. But you should only run `git prune` on a quiescent
+and they'll be gone. (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).
+`git prune` is designed not to cause any harm in such cases of concurrent
+accesses to a repository but you might receive confusing or scary messages.)
[[recovering-from-repository-corruption]]
Recovering from repository corruption
$ git update-index filename
-------------------------------------------------
-but to avoid common mistakes with filename globbing etc, the command
+but to avoid common mistakes with filename globbing etc., the command
will not normally add totally new entries or remove old entries,
i.e. it will normally just update existing cache entries.
result to the file pointed at by `.git/HEAD`, so that we can always see
what the last committed state was.
-Here is an ASCII art by Jon Loeliger that illustrates how
-various pieces fit together.
+Here is a picture that illustrates how various pieces fit together:
------------
Merging multiple trees
----------------------
-Git helps you do a three-way merge, which you can expand to n-way by
-repeating the merge procedure arbitrary times until you finally
-"commit" the state. The normal situation is that you'd only do one
-three-way merge (two parents), and commit it, but if you like to, you
-can do multiple parents in one go.
+Git can help you perform a three-way merge, which can in turn be
+used for a many-way merge by repeating the merge procedure several
+times. The usual situation is that you only do one three-way merge
+(reconciling two lines of history) and commit the result, but if
+you like to, you can merge several branches in one go.
-To do a three-way merge, you need the two sets of "commit" objects
-that you want to merge, use those to find the closest common parent (a
-third "commit" object), and then use those commit objects to find the
-state of the directory ("tree" object) at these points.
+To perform a three-way merge, you start with the two commits you
+want to merge, find their closest common parent (a third commit),
+and compare the trees corresponding to these three commits.
-To get the "base" for the merge, you first look up the common parent
-of two commits with
+To get the "base" for the merge, look up the common parent of two
+commits:
-------------------------------------------------
$ git merge-base <commit1> <commit2>
-------------------------------------------------
-which will return you the commit they are both based on. You should
-now look up the "tree" objects of those commits, which you can easily
-do with (for example)
+This prints the name of a commit they are both based on. You should
+now look up the tree objects of those commits, which you can easily
+do with
-------------------------------------------------
$ git cat-file commit <commitname> | head -1
Earlier we said that trivial merges are done inside
`git read-tree -m`. For example, if the file did not change
-from `$orig` to `HEAD` nor `$target`, or if the file changed
+from `$orig` to `HEAD` or `$target`, or if the file changed
from `$orig` to `HEAD` and `$orig` to `$target` the same way,
obviously the final outcome is what is in `HEAD`. What the
above example shows is that file `hello.c` was changed from
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 SHA-1 of the 'compressed' object.)
As a result, the general consistency of an object can always be tested
independently of the contents or the type of the object: all objects can