--------
[verse]
'git checkout' [-q] [-f] [-m] [<branch>]
+'git checkout' [-q] [-f] [-m] [--detach] [<commit>]
'git checkout' [-q] [-f] [-m] [[-b|-B|--orphan] <new_branch>] [<start_point>]
'git checkout' [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>...
-'git checkout'
--patch [<tree-ish>] [--] [<paths>...]
+'git checkout'
[-p|--patch] [<tree-ish>] [--] [<paths>...]
DESCRIPTION
-----------
'git checkout' [<branch>]::
'git checkout' -b|-B <new_branch> [<start point>]::
+'git checkout' [--detach] [<commit>]::
This form switches branches by updating the index, working
- tree, and HEAD to reflect the specified branch.
+ tree, and HEAD to reflect the specified branch or commit.
+
If `-b` is given, a new branch is created as if linkgit:git-branch[1]
were called and then checked out; in this case you can
that is to say, the branch is not reset/created unless "git checkout" is
successful.
-'git checkout' [--patch] [<tree-ish>] [--] <pathspec>...::
+'git checkout' [-
p|--patch] [<tree-ish>] [--] <pathspec>...::
When <paths> or `--patch` are given, 'git checkout' does *not*
switch branches. It updates the named paths in the working tree
Create the new branch's reflog; see linkgit:git-branch[1] for
details.
+--detach::
+ Rather than checking out a branch to work on it, check out a
+ commit for inspection and discardable experiments.
+ This is the default behavior of "git checkout <commit>" when
+ <commit> is not a branch name. See the "DETACHED HEAD" section
+ below for details.
+
--orphan::
Create a new 'orphan' branch, named <new_branch>, started from
<start_point> and switch to it. The first commit made on this
working tree (and if a <tree-ish> was specified, the index).
+
This means that you can use `git checkout -p` to selectively discard
-edits from your current working tree.
+edits from your current working tree. See the ``Interactive Mode''
+section of linkgit:git-add[1] to learn how to operate the `\--patch` mode.
<branch>::
Branch to checkout; if it refers to a branch (i.e., a name that,
-Detached HEAD
+DETACHED HEAD
-------------
+HEAD normally refers to a named branch (e.g. 'master'). Meanwhile, each
+branch refers to a specific commit. Let's look at a repo with three
+commits, one of them tagged, and with branch 'master' checked out:
+
+------------
+ HEAD (refers to branch 'master')
+ |
+ v
+a---b---c branch 'master' (refers to commit 'c')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
+------------
-It is sometimes useful to be able to 'checkout' a commit that is
-not at the tip of one of your branches. The most obvious
-example is to check out the commit at a tagged official release
-point, like this:
+When a commit is created in this state, the branch is updated to refer to
+the new commit. Specifically, 'git commit' creates a new commit 'd', whose
+parent is commit 'c', and then updates branch 'master' to refer to new
+commit 'd'. HEAD still refers to branch 'master' and so indirectly now refers
+to commit 'd':
------------
-$ git checkout v2.6.18
+$ edit; git add; git commit
+
+ HEAD (refers to branch 'master')
+ |
+ v
+a---b---c---d branch 'master' (refers to commit 'd')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
------------
-Earlier versions of git did not allow this and asked you to
-create a temporary branch using the `-b` option, but starting from
-version 1.5.0, the above command 'detaches' your HEAD from the
-current branch and directly points at the commit named by the tag
-(`v2.6.18` in the example above).
+It is sometimes useful to be able to checkout a commit that is not at
+the tip of any named branch, or even to create a new commit that is not
+referenced by a named branch. Let's look at what happens when we
+checkout commit 'b' (here we show two ways this may be done):
-You can use all git commands while in this state. You can use
-`git reset --hard $othercommit` to further move around, for
-example. You can make changes and create a new commit on top of
-a detached HEAD. You can even create a merge by using `git
-merge $othercommit`.
+------------
+$ git checkout v2.0 # or
+$ git checkout master^^
+
+ HEAD (refers to commit 'b')
+ |
+ v
+a---b---c---d branch 'master' (refers to commit 'd')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
+------------
-The state you are in while your HEAD is detached is not recorded
-by any branch (which is natural --- you are not on any branch).
-What this means is that you can discard your temporary commits
-and merges by switching back to an existing branch (e.g. `git
-checkout master`), and a later `git prune` or `git gc` would
-garbage-collect them. If you did this by mistake, you can ask
-the reflog for HEAD where you were, e.g.
+Notice that regardless of which checkout command we use, HEAD now refers
+directly to commit 'b'. This is known as being in detached HEAD state.
+It means simply that HEAD refers to a specific commit, as opposed to
+referring to a named branch. Let's see what happens when we create a commit:
------------
-$ git log -g -2 HEAD
+$ edit; git add; git commit
+
+ HEAD (refers to commit 'e')
+ |
+ v
+ e
+ /
+a---b---c---d branch 'master' (refers to commit 'd')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
+------------
+
+There is now a new commit 'e', but it is referenced only by HEAD. We can
+of course add yet another commit in this state:
+
+------------
+$ edit; git add; git commit
+
+ HEAD (refers to commit 'f')
+ |
+ v
+ e---f
+ /
+a---b---c---d branch 'master' (refers to commit 'd')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
+------------
+
+In fact, we can perform all the normal git operations. But, let's look
+at what happens when we then checkout master:
+
+------------
+$ git checkout master
+
+ HEAD (refers to branch 'master')
+ e---f |
+ / v
+a---b---c---d branch 'master' (refers to commit 'd')
+ ^
+ |
+ tag 'v2.0' (refers to commit 'b')
------------
+It is important to realize that at this point nothing refers to commit
+'f'. Eventually commit 'f' (and by extension commit 'e') will be deleted
+by the routine git garbage collection process, unless we create a reference
+before that happens. If we have not yet moved away from commit 'f',
+any of these will create a reference to it:
+
+------------
+$ git checkout -b foo <1>
+$ git branch foo <2>
+$ git tag foo <3>
+------------
+
+<1> creates a new branch 'foo', which refers to commit 'f', and then
+updates HEAD to refer to branch 'foo'. In other words, we'll no longer
+be in detached HEAD state after this command.
+
+<2> similarly creates a new branch 'foo', which refers to commit 'f',
+but leaves HEAD detached.
+
+<3> creates a new tag 'foo', which refers to commit 'f',
+leaving HEAD detached.
+
+If we have moved away from commit 'f', then we must first recover its object
+name (typically by using git reflog), and then we can create a reference to
+it. For example, to see the last two commits to which HEAD referred, we
+can use either of these commands:
+
+------------
+$ git reflog -2 HEAD # or
+$ git log -g -2 HEAD
+------------
EXAMPLES
--------
$ git add frotz
------------
-
-Author
-------
-Written by Linus Torvalds <torvalds@osdl.org>
-
-Documentation
---------------
-Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.
-
GIT
---
Part of the linkgit:git[1] suite