Documentation/git-checkout.txt - jrn/git - Git at Google

 git-checkout(1)
 ===============

 NAME
 ----
 git-checkout - Switch branches or restore working tree files

 SYNOPSIS
 --------
 [verse]
 'git checkout' [-q] [-f] [-m] [<branch>]
 'git checkout' [-q] [-f] [-m] --detach [<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' [-p|--patch] [<tree-ish>] [--] [<paths>...]

 DESCRIPTION
 -----------
 Updates files in the working tree to match the version in the index
 or the specified tree.  If no paths are given, 'git checkout' will
 also update `HEAD` to set the specified branch as the current
 branch.

 'git checkout' <branch>::
 	To prepare for working on <branch>, switch to it by updating
 	the index and the files in the working tree, and by pointing
 	HEAD at the branch. Local modifications to the files in the
 	working tree are kept, so that they can be committed to the
 	<branch>.
 +
 If <branch> is not found but there does exist a tracking branch in
 exactly one remote (call it <remote>) with a matching name, treat as
 equivalent to
 +
 ------------
 $ git checkout -b <branch> --track <remote>/<branch>
 ------------
 +
 You could omit <branch>, in which case the command degenerates to
 "check out the current branch", which is a glorified no-op with a
 rather expensive side-effects to show only the tracking information,
 if exists, for the current branch.

 'git checkout' -b|-B <new_branch> [<start point>]::

 	Specifying `-b` causes a new branch to be created as if
 	linkgit:git-branch[1] were called and then checked out.  In
 	this case you can use the `--track` or `--no-track` options,
 	which will be passed to 'git branch'.  As a convenience,
 	`--track` without `-b` implies branch creation; see the
 	description of `--track` below.
 +
 If `-B` is given, <new_branch> is created if it doesn't exist; otherwise, it
 is reset. This is the transactional equivalent of
 +
 ------------
 $ git branch -f <branch> [<start point>]
 $ git checkout <branch>
 ------------
 +
 that is to say, the branch is not reset/created unless "git checkout" is
 successful.

 'git checkout' --detach [<branch>]::
 'git checkout' [--detach] <commit>::

 	Prepare to work on top of <commit>, by detaching HEAD at it
 	(see "DETACHED HEAD" section), and updating the index and the
 	files in the working tree.  Local modifications to the files
 	in the working tree are kept, so that the resulting working
 	tree will be the state recorded in the commit plus the local
 	modifications.
 +
 When the <commit> argument is a branch name, the `--detach` option can
 be used to detach HEAD at the tip of the branch (`git checkout
 <branch>` would check out that branch without detaching HEAD).
 +
 Omitting <branch> detaches HEAD at the tip of the current branch.

 '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
 	from the index file or from a named <tree-ish> (most often a
 	commit).  In this case, the `-b` and `--track` options are
 	meaningless and giving either of them results in an error.  The
 	<tree-ish> argument can be used to specify a specific tree-ish
 	(i.e.  commit, tag or tree) to update the index for the given
 	paths before updating the working tree.
 +
 'git checkout' with <paths> or `--patch` is used to restore modified or
 deleted paths to their original contents from the index or replace paths
 with the contents from a named <tree-ish> (most often a commit-ish).
 +
 The index may contain unmerged entries because of a previous failed merge.
 By default, if you try to check out such an entry from the index, the
 checkout operation will fail and nothing will be checked out.
 Using `-f` will ignore these unmerged entries.  The contents from a
 specific side of the merge can be checked out of the index by
 using `--ours` or `--theirs`.  With `-m`, changes made to the working tree
 file can be discarded to re-create the original conflicted merge result.

 OPTIONS
 -------
 -q::
 --quiet::
 	Quiet, suppress feedback messages.

 -f::
 --force::
 	When switching branches, proceed even if the index or the
 	working tree differs from HEAD.  This is used to throw away
 	local changes.
 +
 When checking out paths from the index, do not fail upon unmerged
 entries; instead, unmerged entries are ignored.

 --ours::
 --theirs::
 	When checking out paths from the index, check out stage #2
 	('ours') or #3 ('theirs') for unmerged paths.

 -b <new_branch>::
 	Create a new branch named <new_branch> and start it at
 	<start_point>; see linkgit:git-branch[1] for details.

 -B <new_branch>::
 	Creates the branch <new_branch> and start it at <start_point>;
 	if it already exists, then reset it to <start_point>. This is
 	equivalent to running "git branch" with "-f"; see
 	linkgit:git-branch[1] for details.

 -t::
 --track::
 	When creating a new branch, set up "upstream" configuration. See
 	"--track" in linkgit:git-branch[1] for details.
 +
 If no '-b' option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
 the initial part up to the "*".
 This would tell us to use "hack" as the local branch when branching
 off of "origin/hack" (or "remotes/origin/hack", or even
 "refs/remotes/origin/hack").  If the given name has no slash, or the above
 guessing results in an empty name, the guessing is aborted.  You can
 explicitly give a name with '-b' in such a case.

 --no-track::
 	Do not set up "upstream" configuration, even if the
 	branch.autoSetupMerge configuration variable is true.

 -l::
 	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 <new_branch>::
 	Create a new 'orphan' branch, named <new_branch>, started from
 	<start_point> and switch to it.  The first commit made on this
 	new branch will have no parents and it will be the root of a new
 	history totally disconnected from all the other branches and
 	commits.
 +
 The index and the working tree are adjusted as if you had previously run
 "git checkout <start_point>".  This allows you to start a new history
 that records a set of paths similar to <start_point> by easily running
 "git commit -a" to make the root commit.
 +
 This can be useful when you want to publish the tree from a commit
 without exposing its full history. You might want to do this to publish
 an open source branch of a project whose current tree is "clean", but
 whose full history contains proprietary or otherwise encumbered bits of
 code.
 +
 If you want to start a disconnected history that records a set of paths
 that is totally different from the one of <start_point>, then you should
 clear the index and the working tree right after creating the orphan
 branch by running "git rm -rf ." from the top level of the working tree.
 Afterwards you will be ready to prepare your new files, repopulating the
 working tree, by copying them from elsewhere, extracting a tarball, etc.

 --ignore-skip-worktree-bits::
 	In sparse checkout mode, `git checkout -- <paths>` would
 	update only entries matched by <paths> and sparse patterns
 	in $GIT_DIR/info/sparse-checkout. This option ignores
 	the sparse patterns and adds back any files in <paths>.

 -m::
 --merge::
 	When switching branches,
 	if you have local modifications to one or more files that
 	are different between the current branch and the branch to
 	which you are switching, the command refuses to switch
 	branches in order to preserve your modifications in context.
 	However, with this option, a three-way merge between the current
 	branch, your working tree contents, and the new branch
 	is done, and you will be on the new branch.
 +
 When a merge conflict happens, the index entries for conflicting
 paths are left unmerged, and you need to resolve the conflicts
 and mark the resolved paths with `git add` (or `git rm` if the merge
 should result in deletion of the path).
 +
 When checking out paths from the index, this option lets you recreate
 the conflicted merge in the specified paths.

 --conflict=<style>::
 	The same as --merge option above, but changes the way the
 	conflicting hunks are presented, overriding the
 	merge.conflictStyle configuration variable.  Possible values are
 	"merge" (default) and "diff3" (in addition to what is shown by
 	"merge" style, shows the original contents).

 -p::
 --patch::
 	Interactively select hunks in the difference between the
 	<tree-ish> (or the index, if unspecified) and the working
 	tree.  The chosen hunks are then applied in reverse to the
 	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. See the ``Interactive Mode''
 section of linkgit:git-add[1] to learn how to operate the `--patch` mode.

 --ignore-other-worktrees::
 	`git checkout` refuses when the wanted ref is already checked
 	out by another worktree. This option makes it check the ref
 	out anyway. In other words, the ref can be held by more than one
 	worktree.

 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
 	branch is checked out. Otherwise, if it refers to a valid
 	commit, your HEAD becomes "detached" and you are no longer on
 	any branch (see below for details).
 +
 As a special case, the `"@{-N}"` syntax for the N-th last branch/commit
 checks out branches (instead of detaching).  You may also specify
 `-` which is synonymous with `"@{-1}"`.
 +
 As a further special case, you may use `"A...B"` as a shortcut for the
 merge base of `A` and `B` if there is exactly one merge base. You can
 leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.

 <new_branch>::
 	Name for the new branch.

 <start_point>::
 	The name of a commit at which to start the new branch; see
 	linkgit:git-branch[1] for details. Defaults to HEAD.

 <tree-ish>::
 	Tree to checkout from (when paths are given). If not specified,
 	the index will be used.


 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')
 ------------

 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':

 ------------
 $ 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')
 ------------

 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):

 ------------
 $ 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')
 ------------

 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:

 ------------
 $ 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
 --------

 . The following sequence checks out the `master` branch, reverts
 the `Makefile` to two revisions back, deletes hello.c by
 mistake, and gets it back from the index.
 +
 ------------
 $ git checkout master             <1>
 $ git checkout master~2 Makefile  <2>
 $ rm -f hello.c
 $ git checkout hello.c            <3>
 ------------
 +
 <1> switch branch
 <2> take a file out of another commit
 <3> restore hello.c from the index
 +
 If you want to check out _all_ C source files out of the index,
 you can say
 +
 ------------
 $ git checkout -- '*.c'
 ------------
 +
 Note the quotes around `*.c`.  The file `hello.c` will also be
 checked out, even though it is no longer in the working tree,
 because the file globbing is used to match entries in the index
 (not in the working tree by the shell).
 +
 If you have an unfortunate branch that is named `hello.c`, this
 step would be confused as an instruction to switch to that branch.
 You should instead write:
 +
 ------------
 $ git checkout -- hello.c
 ------------

 . After working in the wrong branch, switching to the correct
 branch would be done using:
 +
 ------------
 $ git checkout mytopic
 ------------
 +
 However, your "wrong" branch and correct "mytopic" branch may
 differ in files that you have modified locally, in which case
 the above checkout would fail like this:
 +
 ------------
 $ git checkout mytopic
 error: You have local changes to 'frotz'; not switching branches.
 ------------
 +
 You can give the `-m` flag to the command, which would try a
 three-way merge:
 +
 ------------
 $ git checkout -m mytopic
 Auto-merging frotz
 ------------
 +
 After this three-way merge, the local modifications are _not_
 registered in your index file, so `git diff` would show you what
 changes you made since the tip of the new branch.

 . When a merge conflict happens during switching branches with
 the `-m` option, you would see something like this:
 +
 ------------
 $ git checkout -m mytopic
 Auto-merging frotz
 ERROR: Merge conflict in frotz
 fatal: merge program failed
 ------------
 +
 At this point, `git diff` shows the changes cleanly merged as in
 the previous example, as well as the changes in the conflicted
 files.  Edit and resolve the conflict and mark it resolved with
 `git add` as usual:
 +
 ------------
 $ edit frotz
 $ git add frotz
 ------------

 GIT
 ---
 Part of the linkgit:git[1] suite
	git-checkout(1)
	===============

	NAME
	----
	git-checkout - Switch branches or restore working tree files

	SYNOPSIS
	--------
	[verse]
	'git checkout' [-q] [-f] [-m] [<branch>]
	'git checkout' [-q] [-f] [-m] --detach [<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' [-p\|--patch] [<tree-ish>] [--] [<paths>...]

	DESCRIPTION
	-----------
	Updates files in the working tree to match the version in the index
	or the specified tree. If no paths are given, 'git checkout' will
	also update `HEAD` to set the specified branch as the current
	branch.

	'git checkout' <branch>::
	To prepare for working on <branch>, switch to it by updating
	the index and the files in the working tree, and by pointing
	HEAD at the branch. Local modifications to the files in the
	working tree are kept, so that they can be committed to the
	<branch>.
	+
	If <branch> is not found but there does exist a tracking branch in
	exactly one remote (call it <remote>) with a matching name, treat as
	equivalent to
	+
	------------
	$ git checkout -b <branch> --track <remote>/<branch>
	------------
	+
	You could omit <branch>, in which case the command degenerates to
	"check out the current branch", which is a glorified no-op with a
	rather expensive side-effects to show only the tracking information,
	if exists, for the current branch.

	'git checkout' -b\|-B <new_branch> [<start point>]::

	Specifying `-b` causes a new branch to be created as if
	linkgit:git-branch[1] were called and then checked out. In
	this case you can use the `--track` or `--no-track` options,
	which will be passed to 'git branch'. As a convenience,
	`--track` without `-b` implies branch creation; see the
	description of `--track` below.
	+
	If `-B` is given, <new_branch> is created if it doesn't exist; otherwise, it
	is reset. This is the transactional equivalent of
	+
	------------
	$ git branch -f <branch> [<start point>]
	$ git checkout <branch>
	------------
	+
	that is to say, the branch is not reset/created unless "git checkout" is
	successful.

	'git checkout' --detach [<branch>]::
	'git checkout' [--detach] <commit>::

	Prepare to work on top of <commit>, by detaching HEAD at it
	(see "DETACHED HEAD" section), and updating the index and the
	files in the working tree. Local modifications to the files
	in the working tree are kept, so that the resulting working
	tree will be the state recorded in the commit plus the local
	modifications.
	+
	When the <commit> argument is a branch name, the `--detach` option can
	be used to detach HEAD at the tip of the branch (`git checkout
	<branch>` would check out that branch without detaching HEAD).
	+
	Omitting <branch> detaches HEAD at the tip of the current branch.

	'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
	from the index file or from a named <tree-ish> (most often a
	commit). In this case, the `-b` and `--track` options are
	meaningless and giving either of them results in an error. The
	<tree-ish> argument can be used to specify a specific tree-ish
	(i.e. commit, tag or tree) to update the index for the given
	paths before updating the working tree.
	+
	'git checkout' with <paths> or `--patch` is used to restore modified or
	deleted paths to their original contents from the index or replace paths
	with the contents from a named <tree-ish> (most often a commit-ish).
	+
	The index may contain unmerged entries because of a previous failed merge.
	By default, if you try to check out such an entry from the index, the
	checkout operation will fail and nothing will be checked out.
	Using `-f` will ignore these unmerged entries. The contents from a
	specific side of the merge can be checked out of the index by
	using `--ours` or `--theirs`. With `-m`, changes made to the working tree
	file can be discarded to re-create the original conflicted merge result.

	OPTIONS
	-------
	-q::
	--quiet::
	Quiet, suppress feedback messages.

	-f::
	--force::
	When switching branches, proceed even if the index or the
	working tree differs from HEAD. This is used to throw away
	local changes.
	+
	When checking out paths from the index, do not fail upon unmerged
	entries; instead, unmerged entries are ignored.

	--ours::
	--theirs::
	When checking out paths from the index, check out stage #2
	('ours') or #3 ('theirs') for unmerged paths.

	-b <new_branch>::
	Create a new branch named <new_branch> and start it at
	<start_point>; see linkgit:git-branch[1] for details.

	-B <new_branch>::
	Creates the branch <new_branch> and start it at <start_point>;
	if it already exists, then reset it to <start_point>. This is
	equivalent to running "git branch" with "-f"; see
	linkgit:git-branch[1] for details.

	-t::
	--track::
	When creating a new branch, set up "upstream" configuration. See
	"--track" in linkgit:git-branch[1] for details.
	+
	If no '-b' option is given, the name of the new branch will be
	derived from the remote-tracking branch, by looking at the local part of
	the refspec configured for the corresponding remote, and then stripping
	the initial part up to the "*".
	This would tell us to use "hack" as the local branch when branching
	off of "origin/hack" (or "remotes/origin/hack", or even
	"refs/remotes/origin/hack"). If the given name has no slash, or the above
	guessing results in an empty name, the guessing is aborted. You can
	explicitly give a name with '-b' in such a case.

	--no-track::
	Do not set up "upstream" configuration, even if the
	branch.autoSetupMerge configuration variable is true.

	-l::
	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 <new_branch>::
	Create a new 'orphan' branch, named <new_branch>, started from
	<start_point> and switch to it. The first commit made on this
	new branch will have no parents and it will be the root of a new
	history totally disconnected from all the other branches and
	commits.
	+
	The index and the working tree are adjusted as if you had previously run
	"git checkout <start_point>". This allows you to start a new history
	that records a set of paths similar to <start_point> by easily running
	"git commit -a" to make the root commit.
	+
	This can be useful when you want to publish the tree from a commit
	without exposing its full history. You might want to do this to publish
	an open source branch of a project whose current tree is "clean", but
	whose full history contains proprietary or otherwise encumbered bits of
	code.
	+
	If you want to start a disconnected history that records a set of paths
	that is totally different from the one of <start_point>, then you should
	clear the index and the working tree right after creating the orphan
	branch by running "git rm -rf ." from the top level of the working tree.
	Afterwards you will be ready to prepare your new files, repopulating the
	working tree, by copying them from elsewhere, extracting a tarball, etc.

	--ignore-skip-worktree-bits::
	In sparse checkout mode, `git checkout -- <paths>` would
	update only entries matched by <paths> and sparse patterns
	in $GIT_DIR/info/sparse-checkout. This option ignores
	the sparse patterns and adds back any files in <paths>.

	-m::
	--merge::
	When switching branches,
	if you have local modifications to one or more files that
	are different between the current branch and the branch to
	which you are switching, the command refuses to switch
	branches in order to preserve your modifications in context.
	However, with this option, a three-way merge between the current
	branch, your working tree contents, and the new branch
	is done, and you will be on the new branch.
	+
	When a merge conflict happens, the index entries for conflicting
	paths are left unmerged, and you need to resolve the conflicts
	and mark the resolved paths with `git add` (or `git rm` if the merge
	should result in deletion of the path).
	+
	When checking out paths from the index, this option lets you recreate
	the conflicted merge in the specified paths.

	--conflict=<style>::
	The same as --merge option above, but changes the way the
	conflicting hunks are presented, overriding the
	merge.conflictStyle configuration variable. Possible values are
	"merge" (default) and "diff3" (in addition to what is shown by
	"merge" style, shows the original contents).

	-p::
	--patch::
	Interactively select hunks in the difference between the
	<tree-ish> (or the index, if unspecified) and the working
	tree. The chosen hunks are then applied in reverse to the
	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. See the ``Interactive Mode''
	section of linkgit:git-add[1] to learn how to operate the `--patch` mode.

	--ignore-other-worktrees::
	`git checkout` refuses when the wanted ref is already checked
	out by another worktree. This option makes it check the ref
	out anyway. In other words, the ref can be held by more than one
	worktree.

	<branch>::
	Branch to checkout; if it refers to a branch (i.e., a name that,
	when prepended with "refs/heads/", is a valid ref), then that
	branch is checked out. Otherwise, if it refers to a valid
	commit, your HEAD becomes "detached" and you are no longer on
	any branch (see below for details).
	+
	As a special case, the `"@{-N}"` syntax for the N-th last branch/commit
	checks out branches (instead of detaching). You may also specify
	`-` which is synonymous with `"@{-1}"`.
	+
	As a further special case, you may use `"A...B"` as a shortcut for the
	merge base of `A` and `B` if there is exactly one merge base. You can
	leave out at most one of `A` and `B`, in which case it defaults to `HEAD`.

	<new_branch>::
	Name for the new branch.

	<start_point>::
	The name of a commit at which to start the new branch; see
	linkgit:git-branch[1] for details. Defaults to HEAD.

	<tree-ish>::
	Tree to checkout from (when paths are given). If not specified,
	the index will be used.



	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')
	------------

	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':

	------------
	$ 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')
	------------

	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):

	------------
	$ 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')
	------------

	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:

	------------
	$ 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
	--------

	. The following sequence checks out the `master` branch, reverts
	the `Makefile` to two revisions back, deletes hello.c by
	mistake, and gets it back from the index.
	+
	------------
	$ git checkout master <1>
	$ git checkout master~2 Makefile <2>
	$ rm -f hello.c
	$ git checkout hello.c <3>
	------------
	+
	<1> switch branch
	<2> take a file out of another commit
	<3> restore hello.c from the index
	+
	If you want to check out _all_ C source files out of the index,
	you can say
	+
	------------
	$ git checkout -- '*.c'
	------------
	+
	Note the quotes around `*.c`. The file `hello.c` will also be
	checked out, even though it is no longer in the working tree,
	because the file globbing is used to match entries in the index
	(not in the working tree by the shell).
	+
	If you have an unfortunate branch that is named `hello.c`, this
	step would be confused as an instruction to switch to that branch.
	You should instead write:
	+
	------------
	$ git checkout -- hello.c
	------------

	. After working in the wrong branch, switching to the correct
	branch would be done using:
	+
	------------
	$ git checkout mytopic
	------------
	+
	However, your "wrong" branch and correct "mytopic" branch may
	differ in files that you have modified locally, in which case
	the above checkout would fail like this:
	+
	------------
	$ git checkout mytopic
	error: You have local changes to 'frotz'; not switching branches.
	------------
	+
	You can give the `-m` flag to the command, which would try a
	three-way merge:
	+
	------------
	$ git checkout -m mytopic
	Auto-merging frotz
	------------
	+
	After this three-way merge, the local modifications are _not_
	registered in your index file, so `git diff` would show you what
	changes you made since the tip of the new branch.

	. When a merge conflict happens during switching branches with
	the `-m` option, you would see something like this:
	+
	------------
	$ git checkout -m mytopic
	Auto-merging frotz
	ERROR: Merge conflict in frotz
	fatal: merge program failed
	------------
	+
	At this point, `git diff` shows the changes cleanly merged as in
	the previous example, as well as the changes in the conflicted
	files. Edit and resolve the conflict and mark it resolved with
	`git add` as usual:
	+
	------------
	$ edit frotz
	$ git add frotz
	------------

	GIT
	---
	Part of the linkgit:git[1] suite