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

 githooks(5)
 ===========

 NAME
 ----
 githooks - Hooks used by Git

 SYNOPSIS
 --------
 $GIT_DIR/hooks/* (or \`git config core.hooksPath`/*)


 DESCRIPTION
 -----------

 Hooks are programs you can place in a hooks directory to trigger
 actions at certain points in git's execution. Hooks that don't have
 the executable bit set are ignored.

 By default the hooks directory is `$GIT_DIR/hooks`, but that can be
 changed via the `core.hooksPath` configuration variable (see
 linkgit:git-config[1]).

 Before Git invokes a hook, it changes its working directory to either
 $GIT_DIR in a bare repository or the root of the working tree in a non-bare
 repository. An exception are hooks triggered during a push ('pre-receive',
 'update', 'post-receive', 'post-update', 'push-to-checkout') which are always
 executed in $GIT_DIR.

 Hooks can get their arguments via the environment, command-line
 arguments, and stdin. See the documentation for each hook below for
 details.

 'git init' may copy hooks to the new repository, depending on its
 configuration. See the "TEMPLATE DIRECTORY" section in
 linkgit:git-init[1] for details. When the rest of this document refers
 to "default hooks" it's talking about the default template shipped
 with Git.

 The currently supported hooks are described below.

 HOOKS
 -----

 applypatch-msg
 ~~~~~~~~~~~~~~

 This hook is invoked by 'git am'.  It takes a single
 parameter, the name of the file that holds the proposed commit
 log message.  Exiting with a non-zero status causes 'git am' to abort
 before applying the patch.

 The hook is allowed to edit the message file in place, and can
 be used to normalize the message into some project standard
 format. It can also be used to refuse the commit after inspecting
 the message file.

 The default 'applypatch-msg' hook, when enabled, runs the
 'commit-msg' hook, if the latter is enabled.

 pre-applypatch
 ~~~~~~~~~~~~~~

 This hook is invoked by 'git am'.  It takes no parameter, and is
 invoked after the patch is applied, but before a commit is made.

 If it exits with non-zero status, then the working tree will not be
 committed after applying the patch.

 It can be used to inspect the current working tree and refuse to
 make a commit if it does not pass certain test.

 The default 'pre-applypatch' hook, when enabled, runs the
 'pre-commit' hook, if the latter is enabled.

 post-applypatch
 ~~~~~~~~~~~~~~~

 This hook is invoked by 'git am'.  It takes no parameter,
 and is invoked after the patch is applied and a commit is made.

 This hook is meant primarily for notification, and cannot affect
 the outcome of 'git am'.

 pre-commit
 ~~~~~~~~~~

 This hook is invoked by 'git commit', and can be bypassed
 with the `--no-verify` option.  It takes no parameters, and is
 invoked before obtaining the proposed commit log message and
 making a commit.  Exiting with a non-zero status from this script
 causes the 'git commit' command to abort before creating a commit.

 The default 'pre-commit' hook, when enabled, catches introduction
 of lines with trailing whitespaces and aborts the commit when
 such a line is found.

 All the 'git commit' hooks are invoked with the environment
 variable `GIT_EDITOR=:` if the command will not bring up an editor
 to modify the commit message.

 prepare-commit-msg
 ~~~~~~~~~~~~~~~~~~

 This hook is invoked by 'git commit' right after preparing the
 default log message, and before the editor is started.

 It takes one to three parameters.  The first is the name of the file
 that contains the commit log message.  The second is the source of the commit
 message, and can be: `message` (if a `-m` or `-F` option was
 given); `template` (if a `-t` option was given or the
 configuration option `commit.template` is set); `merge` (if the
 commit is a merge or a `.git/MERGE_MSG` file exists); `squash`
 (if a `.git/SQUASH_MSG` file exists); or `commit`, followed by
 a commit SHA-1 (if a `-c`, `-C` or `--amend` option was given).

 If the exit status is non-zero, 'git commit' will abort.

 The purpose of the hook is to edit the message file in place, and
 it is not suppressed by the `--no-verify` option.  A non-zero exit
 means a failure of the hook and aborts the commit.  It should not
 be used as replacement for pre-commit hook.

 The sample `prepare-commit-msg` hook that comes with Git removes the
 help message found in the commented portion of the commit template.

 commit-msg
 ~~~~~~~~~~

 This hook is invoked by 'git commit' and 'git merge', and can be
 bypassed with the `--no-verify` option.  It takes a single parameter,
 the name of the file that holds the proposed commit log message.
 Exiting with a non-zero status causes the command to abort.

 The hook is allowed to edit the message file in place, and can be used
 to normalize the message into some project standard format. It
 can also be used to refuse the commit after inspecting the message
 file.

 The default 'commit-msg' hook, when enabled, detects duplicate
 "Signed-off-by" lines, and aborts the commit if one is found.

 post-commit
 ~~~~~~~~~~~

 This hook is invoked by 'git commit'. It takes no parameters, and is
 invoked after a commit is made.

 This hook is meant primarily for notification, and cannot affect
 the outcome of 'git commit'.

 pre-rebase
 ~~~~~~~~~~

 This hook is called by 'git rebase' and can be used to prevent a
 branch from getting rebased.  The hook may be called with one or
 two parameters.  The first parameter is the upstream from which
 the series was forked.  The second parameter is the branch being
 rebased, and is not set when rebasing the current branch.

 post-checkout
 ~~~~~~~~~~~~~

 This hook is invoked when a 'git checkout' is run after having updated the
 worktree.  The hook is given three parameters: the ref of the previous HEAD,
 the ref of the new HEAD (which may or may not have changed), and a flag
 indicating whether the checkout was a branch checkout (changing branches,
 flag=1) or a file checkout (retrieving a file from the index, flag=0).
 This hook cannot affect the outcome of 'git checkout'.

 It is also run after 'git clone', unless the --no-checkout (-n) option is
 used. The first parameter given to the hook is the null-ref, the second the
 ref of the new HEAD and the flag is always 1.

 This hook can be used to perform repository validity checks, auto-display
 differences from the previous HEAD if different, or set working dir metadata
 properties.

 post-merge
 ~~~~~~~~~~

 This hook is invoked by 'git merge', which happens when a 'git pull'
 is done on a local repository.  The hook takes a single parameter, a status
 flag specifying whether or not the merge being done was a squash merge.
 This hook cannot affect the outcome of 'git merge' and is not executed,
 if the merge failed due to conflicts.

 This hook can be used in conjunction with a corresponding pre-commit hook to
 save and restore any form of metadata associated with the working tree
 (e.g.: permissions/ownership, ACLS, etc).  See contrib/hooks/setgitperms.perl
 for an example of how to do this.

 pre-push
 ~~~~~~~~

 This hook is called by 'git push' and can be used to prevent a push from taking
 place.  The hook is called with two parameters which provide the name and
 location of the destination remote, if a named remote is not being used both
 values will be the same.

 Information about what is to be pushed is provided on the hook's standard
 input with lines of the form:

   <local ref> SP <local sha1> SP <remote ref> SP <remote sha1> LF

 For instance, if the command +git push origin master:foreign+ were run the
 hook would receive a line like the following:

   refs/heads/master 67890 refs/heads/foreign 12345

 although the full, 40-character SHA-1s would be supplied.  If the foreign ref
 does not yet exist the `<remote SHA-1>` will be 40 `0`.  If a ref is to be
 deleted, the `<local ref>` will be supplied as `(delete)` and the `<local
 SHA-1>` will be 40 `0`.  If the local commit was specified by something other
 than a name which could be expanded (such as `HEAD~`, or a SHA-1) it will be
 supplied as it was originally given.

 If this hook exits with a non-zero status, 'git push' will abort without
 pushing anything.  Information about why the push is rejected may be sent
 to the user by writing to standard error.

 [[pre-receive]]
 pre-receive
 ~~~~~~~~~~~

 This hook is invoked by 'git-receive-pack' on the remote repository,
 which happens when a 'git push' is done on a local repository.
 Just before starting to update refs on the remote repository, the
 pre-receive hook is invoked.  Its exit status determines the success
 or failure of the update.

 This hook executes once for the receive operation. It takes no
 arguments, but for each ref to be updated it receives on standard
 input a line of the format:

   <old-value> SP <new-value> SP <ref-name> LF

 where `<old-value>` is the old object name stored in the ref,
 `<new-value>` is the new object name to be stored in the ref and
 `<ref-name>` is the full name of the ref.
 When creating a new ref, `<old-value>` is 40 `0`.

 If the hook exits with non-zero status, none of the refs will be
 updated. If the hook exits with zero, updating of individual refs can
 still be prevented by the <<update,'update'>> hook.

 Both standard output and standard error output are forwarded to
 'git send-pack' on the other end, so you can simply `echo` messages
 for the user.

 The number of push options given on the command line of
 `git push --push-option=...` can be read from the environment
 variable `GIT_PUSH_OPTION_COUNT`, and the options themselves are
 found in `GIT_PUSH_OPTION_0`, `GIT_PUSH_OPTION_1`,...
 If it is negotiated to not use the push options phase, the
 environment variables will not be set. If the client selects
 to use push options, but doesn't transmit any, the count variable
 will be set to zero, `GIT_PUSH_OPTION_COUNT=0`.

 See the section on "Quarantine Environment" in
 linkgit:git-receive-pack[1] for some caveats.

 [[update]]
 update
 ~~~~~~

 This hook is invoked by 'git-receive-pack' on the remote repository,
 which happens when a 'git push' is done on a local repository.
 Just before updating the ref on the remote repository, the update hook
 is invoked.  Its exit status determines the success or failure of
 the ref update.

 The hook executes once for each ref to be updated, and takes
 three parameters:

  - the name of the ref being updated,
  - the old object name stored in the ref,
  - and the new object name to be stored in the ref.

 A zero exit from the update hook allows the ref to be updated.
 Exiting with a non-zero status prevents 'git-receive-pack'
 from updating that ref.

 This hook can be used to prevent 'forced' update on certain refs by
 making sure that the object name is a commit object that is a
 descendant of the commit object named by the old object name.
 That is, to enforce a "fast-forward only" policy.

 It could also be used to log the old..new status.  However, it
 does not know the entire set of branches, so it would end up
 firing one e-mail per ref when used naively, though.  The
 <<post-receive,'post-receive'>> hook is more suited to that.

 In an environment that restricts the users' access only to git
 commands over the wire, this hook can be used to implement access
 control without relying on filesystem ownership and group
 membership. See linkgit:git-shell[1] for how you might use the login
 shell to restrict the user's access to only git commands.

 Both standard output and standard error output are forwarded to
 'git send-pack' on the other end, so you can simply `echo` messages
 for the user.

 The default 'update' hook, when enabled--and with
 `hooks.allowunannotated` config option unset or set to false--prevents
 unannotated tags to be pushed.

 [[post-receive]]
 post-receive
 ~~~~~~~~~~~~

 This hook is invoked by 'git-receive-pack' on the remote repository,
 which happens when a 'git push' is done on a local repository.
 It executes on the remote repository once after all the refs have
 been updated.

 This hook executes once for the receive operation.  It takes no
 arguments, but gets the same information as the
 <<pre-receive,'pre-receive'>>
 hook does on its standard input.

 This hook does not affect the outcome of 'git-receive-pack', as it
 is called after the real work is done.

 This supersedes the <<post-update,'post-update'>> hook in that it gets
 both old and new values of all the refs in addition to their
 names.

 Both standard output and standard error output are forwarded to
 'git send-pack' on the other end, so you can simply `echo` messages
 for the user.

 The default 'post-receive' hook is empty, but there is
 a sample script `post-receive-email` provided in the `contrib/hooks`
 directory in Git distribution, which implements sending commit
 emails.

 The number of push options given on the command line of
 `git push --push-option=...` can be read from the environment
 variable `GIT_PUSH_OPTION_COUNT`, and the options themselves are
 found in `GIT_PUSH_OPTION_0`, `GIT_PUSH_OPTION_1`,...
 If it is negotiated to not use the push options phase, the
 environment variables will not be set. If the client selects
 to use push options, but doesn't transmit any, the count variable
 will be set to zero, `GIT_PUSH_OPTION_COUNT=0`.

 [[post-update]]
 post-update
 ~~~~~~~~~~~

 This hook is invoked by 'git-receive-pack' on the remote repository,
 which happens when a 'git push' is done on a local repository.
 It executes on the remote repository once after all the refs have
 been updated.

 It takes a variable number of parameters, each of which is the
 name of ref that was actually updated.

 This hook is meant primarily for notification, and cannot affect
 the outcome of 'git-receive-pack'.

 The 'post-update' hook can tell what are the heads that were pushed,
 but it does not know what their original and updated values are,
 so it is a poor place to do log old..new. The
 <<post-receive,'post-receive'>> hook does get both original and
 updated values of the refs. You might consider it instead if you need
 them.

 When enabled, the default 'post-update' hook runs
 'git update-server-info' to keep the information used by dumb
 transports (e.g., HTTP) up to date.  If you are publishing
 a Git repository that is accessible via HTTP, you should
 probably enable this hook.

 Both standard output and standard error output are forwarded to
 'git send-pack' on the other end, so you can simply `echo` messages
 for the user.

 push-to-checkout
 ~~~~~~~~~~~~~~~~

 This hook is invoked by 'git-receive-pack' on the remote repository,
 which happens when a 'git push' is done on a local repository, when
 the push tries to update the branch that is currently checked out
 and the `receive.denyCurrentBranch` configuration variable is set to
 `updateInstead`.  Such a push by default is refused if the working
 tree and the index of the remote repository has any difference from
 the currently checked out commit; when both the working tree and the
 index match the current commit, they are updated to match the newly
 pushed tip of the branch.  This hook is to be used to override the
 default behaviour.

 The hook receives the commit with which the tip of the current
 branch is going to be updated.  It can exit with a non-zero status
 to refuse the push (when it does so, it must not modify the index or
 the working tree).  Or it can make any necessary changes to the
 working tree and to the index to bring them to the desired state
 when the tip of the current branch is updated to the new commit, and
 exit with a zero status.

 For example, the hook can simply run `git read-tree -u -m HEAD "$1"`
 in order to emulate 'git fetch' that is run in the reverse direction
 with `git push`, as the two-tree form of `read-tree -u -m` is
 essentially the same as `git checkout` that switches branches while
 keeping the local changes in the working tree that do not interfere
 with the difference between the branches.


 pre-auto-gc
 ~~~~~~~~~~~

 This hook is invoked by 'git gc --auto'. It takes no parameter, and
 exiting with non-zero status from this script causes the 'git gc --auto'
 to abort.

 post-rewrite
 ~~~~~~~~~~~~

 This hook is invoked by commands that rewrite commits (`git commit
 --amend`, 'git-rebase'; currently 'git-filter-branch' does 'not' call
 it!).  Its first argument denotes the command it was invoked by:
 currently one of `amend` or `rebase`.  Further command-dependent
 arguments may be passed in the future.

 The hook receives a list of the rewritten commits on stdin, in the
 format

   <old-sha1> SP <new-sha1> [ SP <extra-info> ] LF

 The 'extra-info' is again command-dependent.  If it is empty, the
 preceding SP is also omitted.  Currently, no commands pass any
 'extra-info'.

 The hook always runs after the automatic note copying (see
 "notes.rewrite.<command>" in linkgit:git-config[1]) has happened, and
 thus has access to these notes.

 The following command-specific comments apply:

 rebase::
 	For the 'squash' and 'fixup' operation, all commits that were
 	squashed are listed as being rewritten to the squashed commit.
 	This means that there will be several lines sharing the same
 	'new-sha1'.
 +
 The commits are guaranteed to be listed in the order that they were
 processed by rebase.

 sendemail-validate
 ~~~~~~~~~~~~~~~~~~

 This hook is invoked by 'git send-email'.  It takes a single parameter,
 the name of the file that holds the e-mail to be sent.  Exiting with a
 non-zero status causes 'git send-email' to abort before sending any
 e-mails.


 GIT
 ---
 Part of the linkgit:git[1] suite
	githooks(5)
	===========

	NAME
	----
	githooks - Hooks used by Git

	SYNOPSIS
	--------
	$GIT_DIR/hooks/* (or \`git config core.hooksPath`/*)


	DESCRIPTION
	-----------

	Hooks are programs you can place in a hooks directory to trigger
	actions at certain points in git's execution. Hooks that don't have
	the executable bit set are ignored.

	By default the hooks directory is `$GIT_DIR/hooks`, but that can be
	changed via the `core.hooksPath` configuration variable (see
	linkgit:git-config[1]).

	Before Git invokes a hook, it changes its working directory to either
	$GIT_DIR in a bare repository or the root of the working tree in a non-bare
	repository. An exception are hooks triggered during a push ('pre-receive',
	'update', 'post-receive', 'post-update', 'push-to-checkout') which are always
	executed in $GIT_DIR.

	Hooks can get their arguments via the environment, command-line
	arguments, and stdin. See the documentation for each hook below for
	details.

	'git init' may copy hooks to the new repository, depending on its
	configuration. See the "TEMPLATE DIRECTORY" section in
	linkgit:git-init[1] for details. When the rest of this document refers
	to "default hooks" it's talking about the default template shipped
	with Git.

	The currently supported hooks are described below.

	HOOKS
	-----

	applypatch-msg
	~~~~~~~~~~~~~~

	This hook is invoked by 'git am'. It takes a single
	parameter, the name of the file that holds the proposed commit
	log message. Exiting with a non-zero status causes 'git am' to abort
	before applying the patch.

	The hook is allowed to edit the message file in place, and can
	be used to normalize the message into some project standard
	format. It can also be used to refuse the commit after inspecting
	the message file.

	The default 'applypatch-msg' hook, when enabled, runs the
	'commit-msg' hook, if the latter is enabled.

	pre-applypatch
	~~~~~~~~~~~~~~

	This hook is invoked by 'git am'. It takes no parameter, and is
	invoked after the patch is applied, but before a commit is made.

	If it exits with non-zero status, then the working tree will not be
	committed after applying the patch.

	It can be used to inspect the current working tree and refuse to
	make a commit if it does not pass certain test.

	The default 'pre-applypatch' hook, when enabled, runs the
	'pre-commit' hook, if the latter is enabled.

	post-applypatch
	~~~~~~~~~~~~~~~

	This hook is invoked by 'git am'. It takes no parameter,
	and is invoked after the patch is applied and a commit is made.

	This hook is meant primarily for notification, and cannot affect
	the outcome of 'git am'.

	pre-commit
	~~~~~~~~~~

	This hook is invoked by 'git commit', and can be bypassed
	with the `--no-verify` option. It takes no parameters, and is
	invoked before obtaining the proposed commit log message and
	making a commit. Exiting with a non-zero status from this script
	causes the 'git commit' command to abort before creating a commit.

	The default 'pre-commit' hook, when enabled, catches introduction
	of lines with trailing whitespaces and aborts the commit when
	such a line is found.

	All the 'git commit' hooks are invoked with the environment
	variable `GIT_EDITOR=:` if the command will not bring up an editor
	to modify the commit message.

	prepare-commit-msg
	~~~~~~~~~~~~~~~~~~

	This hook is invoked by 'git commit' right after preparing the
	default log message, and before the editor is started.

	It takes one to three parameters. The first is the name of the file
	that contains the commit log message. The second is the source of the commit
	message, and can be: `message` (if a `-m` or `-F` option was
	given); `template` (if a `-t` option was given or the
	configuration option `commit.template` is set); `merge` (if the
	commit is a merge or a `.git/MERGE_MSG` file exists); `squash`
	(if a `.git/SQUASH_MSG` file exists); or `commit`, followed by
	a commit SHA-1 (if a `-c`, `-C` or `--amend` option was given).

	If the exit status is non-zero, 'git commit' will abort.

	The purpose of the hook is to edit the message file in place, and
	it is not suppressed by the `--no-verify` option. A non-zero exit
	means a failure of the hook and aborts the commit. It should not
	be used as replacement for pre-commit hook.

	The sample `prepare-commit-msg` hook that comes with Git removes the
	help message found in the commented portion of the commit template.

	commit-msg
	~~~~~~~~~~

	This hook is invoked by 'git commit' and 'git merge', and can be
	bypassed with the `--no-verify` option. It takes a single parameter,
	the name of the file that holds the proposed commit log message.
	Exiting with a non-zero status causes the command to abort.

	The hook is allowed to edit the message file in place, and can be used
	to normalize the message into some project standard format. It
	can also be used to refuse the commit after inspecting the message
	file.

	The default 'commit-msg' hook, when enabled, detects duplicate
	"Signed-off-by" lines, and aborts the commit if one is found.

	post-commit
	~~~~~~~~~~~

	This hook is invoked by 'git commit'. It takes no parameters, and is
	invoked after a commit is made.

	This hook is meant primarily for notification, and cannot affect
	the outcome of 'git commit'.

	pre-rebase
	~~~~~~~~~~

	This hook is called by 'git rebase' and can be used to prevent a
	branch from getting rebased. The hook may be called with one or
	two parameters. The first parameter is the upstream from which
	the series was forked. The second parameter is the branch being
	rebased, and is not set when rebasing the current branch.

	post-checkout
	~~~~~~~~~~~~~

	This hook is invoked when a 'git checkout' is run after having updated the
	worktree. The hook is given three parameters: the ref of the previous HEAD,
	the ref of the new HEAD (which may or may not have changed), and a flag
	indicating whether the checkout was a branch checkout (changing branches,
	flag=1) or a file checkout (retrieving a file from the index, flag=0).
	This hook cannot affect the outcome of 'git checkout'.

	It is also run after 'git clone', unless the --no-checkout (-n) option is
	used. The first parameter given to the hook is the null-ref, the second the
	ref of the new HEAD and the flag is always 1.

	This hook can be used to perform repository validity checks, auto-display
	differences from the previous HEAD if different, or set working dir metadata
	properties.

	post-merge
	~~~~~~~~~~

	This hook is invoked by 'git merge', which happens when a 'git pull'
	is done on a local repository. The hook takes a single parameter, a status
	flag specifying whether or not the merge being done was a squash merge.
	This hook cannot affect the outcome of 'git merge' and is not executed,
	if the merge failed due to conflicts.

	This hook can be used in conjunction with a corresponding pre-commit hook to
	save and restore any form of metadata associated with the working tree
	(e.g.: permissions/ownership, ACLS, etc). See contrib/hooks/setgitperms.perl
	for an example of how to do this.

	pre-push
	~~~~~~~~

	This hook is called by 'git push' and can be used to prevent a push from taking
	place. The hook is called with two parameters which provide the name and
	location of the destination remote, if a named remote is not being used both
	values will be the same.

	Information about what is to be pushed is provided on the hook's standard
	input with lines of the form:

	<local ref> SP <local sha1> SP <remote ref> SP <remote sha1> LF

	For instance, if the command +git push origin master:foreign+ were run the
	hook would receive a line like the following:

	refs/heads/master 67890 refs/heads/foreign 12345

	although the full, 40-character SHA-1s would be supplied. If the foreign ref
	does not yet exist the `<remote SHA-1>` will be 40 `0`. If a ref is to be
	deleted, the `<local ref>` will be supplied as `(delete)` and the `<local
	SHA-1>` will be 40 `0`. If the local commit was specified by something other
	than a name which could be expanded (such as `HEAD~`, or a SHA-1) it will be
	supplied as it was originally given.

	If this hook exits with a non-zero status, 'git push' will abort without
	pushing anything. Information about why the push is rejected may be sent
	to the user by writing to standard error.

	[[pre-receive]]
	pre-receive
	~~~~~~~~~~~

	This hook is invoked by 'git-receive-pack' on the remote repository,
	which happens when a 'git push' is done on a local repository.
	Just before starting to update refs on the remote repository, the
	pre-receive hook is invoked. Its exit status determines the success
	or failure of the update.

	This hook executes once for the receive operation. It takes no
	arguments, but for each ref to be updated it receives on standard
	input a line of the format:

	<old-value> SP <new-value> SP <ref-name> LF

	where `<old-value>` is the old object name stored in the ref,
	`<new-value>` is the new object name to be stored in the ref and
	`<ref-name>` is the full name of the ref.
	When creating a new ref, `<old-value>` is 40 `0`.

	If the hook exits with non-zero status, none of the refs will be
	updated. If the hook exits with zero, updating of individual refs can
	still be prevented by the <<update,'update'>> hook.

	Both standard output and standard error output are forwarded to
	'git send-pack' on the other end, so you can simply `echo` messages
	for the user.

	The number of push options given on the command line of
	`git push --push-option=...` can be read from the environment
	variable `GIT_PUSH_OPTION_COUNT`, and the options themselves are
	found in `GIT_PUSH_OPTION_0`, `GIT_PUSH_OPTION_1`,...
	If it is negotiated to not use the push options phase, the
	environment variables will not be set. If the client selects
	to use push options, but doesn't transmit any, the count variable
	will be set to zero, `GIT_PUSH_OPTION_COUNT=0`.

	See the section on "Quarantine Environment" in
	linkgit:git-receive-pack[1] for some caveats.

	[[update]]
	update
	~~~~~~

	This hook is invoked by 'git-receive-pack' on the remote repository,
	which happens when a 'git push' is done on a local repository.
	Just before updating the ref on the remote repository, the update hook
	is invoked. Its exit status determines the success or failure of
	the ref update.

	The hook executes once for each ref to be updated, and takes
	three parameters:

	- the name of the ref being updated,
	- the old object name stored in the ref,
	- and the new object name to be stored in the ref.

	A zero exit from the update hook allows the ref to be updated.
	Exiting with a non-zero status prevents 'git-receive-pack'
	from updating that ref.

	This hook can be used to prevent 'forced' update on certain refs by
	making sure that the object name is a commit object that is a
	descendant of the commit object named by the old object name.
	That is, to enforce a "fast-forward only" policy.

	It could also be used to log the old..new status. However, it
	does not know the entire set of branches, so it would end up
	firing one e-mail per ref when used naively, though. The
	<<post-receive,'post-receive'>> hook is more suited to that.

	In an environment that restricts the users' access only to git
	commands over the wire, this hook can be used to implement access
	control without relying on filesystem ownership and group
	membership. See linkgit:git-shell[1] for how you might use the login
	shell to restrict the user's access to only git commands.

	Both standard output and standard error output are forwarded to
	'git send-pack' on the other end, so you can simply `echo` messages
	for the user.

	The default 'update' hook, when enabled--and with
	`hooks.allowunannotated` config option unset or set to false--prevents
	unannotated tags to be pushed.

	[[post-receive]]
	post-receive
	~~~~~~~~~~~~

	This hook is invoked by 'git-receive-pack' on the remote repository,
	which happens when a 'git push' is done on a local repository.
	It executes on the remote repository once after all the refs have
	been updated.

	This hook executes once for the receive operation. It takes no
	arguments, but gets the same information as the
	<<pre-receive,'pre-receive'>>
	hook does on its standard input.

	This hook does not affect the outcome of 'git-receive-pack', as it
	is called after the real work is done.

	This supersedes the <<post-update,'post-update'>> hook in that it gets
	both old and new values of all the refs in addition to their
	names.

	Both standard output and standard error output are forwarded to
	'git send-pack' on the other end, so you can simply `echo` messages
	for the user.

	The default 'post-receive' hook is empty, but there is
	a sample script `post-receive-email` provided in the `contrib/hooks`
	directory in Git distribution, which implements sending commit
	emails.

	The number of push options given on the command line of
	`git push --push-option=...` can be read from the environment
	variable `GIT_PUSH_OPTION_COUNT`, and the options themselves are
	found in `GIT_PUSH_OPTION_0`, `GIT_PUSH_OPTION_1`,...
	If it is negotiated to not use the push options phase, the
	environment variables will not be set. If the client selects
	to use push options, but doesn't transmit any, the count variable
	will be set to zero, `GIT_PUSH_OPTION_COUNT=0`.

	[[post-update]]
	post-update
	~~~~~~~~~~~

	This hook is invoked by 'git-receive-pack' on the remote repository,
	which happens when a 'git push' is done on a local repository.
	It executes on the remote repository once after all the refs have
	been updated.

	It takes a variable number of parameters, each of which is the
	name of ref that was actually updated.

	This hook is meant primarily for notification, and cannot affect
	the outcome of 'git-receive-pack'.

	The 'post-update' hook can tell what are the heads that were pushed,
	but it does not know what their original and updated values are,
	so it is a poor place to do log old..new. The
	<<post-receive,'post-receive'>> hook does get both original and
	updated values of the refs. You might consider it instead if you need
	them.

	When enabled, the default 'post-update' hook runs
	'git update-server-info' to keep the information used by dumb
	transports (e.g., HTTP) up to date. If you are publishing
	a Git repository that is accessible via HTTP, you should
	probably enable this hook.

	Both standard output and standard error output are forwarded to
	'git send-pack' on the other end, so you can simply `echo` messages
	for the user.

	push-to-checkout
	~~~~~~~~~~~~~~~~

	This hook is invoked by 'git-receive-pack' on the remote repository,
	which happens when a 'git push' is done on a local repository, when
	the push tries to update the branch that is currently checked out
	and the `receive.denyCurrentBranch` configuration variable is set to
	`updateInstead`. Such a push by default is refused if the working
	tree and the index of the remote repository has any difference from
	the currently checked out commit; when both the working tree and the
	index match the current commit, they are updated to match the newly
	pushed tip of the branch. This hook is to be used to override the
	default behaviour.

	The hook receives the commit with which the tip of the current
	branch is going to be updated. It can exit with a non-zero status
	to refuse the push (when it does so, it must not modify the index or
	the working tree). Or it can make any necessary changes to the
	working tree and to the index to bring them to the desired state
	when the tip of the current branch is updated to the new commit, and
	exit with a zero status.

	For example, the hook can simply run `git read-tree -u -m HEAD "$1"`
	in order to emulate 'git fetch' that is run in the reverse direction
	with `git push`, as the two-tree form of `read-tree -u -m` is
	essentially the same as `git checkout` that switches branches while
	keeping the local changes in the working tree that do not interfere
	with the difference between the branches.


	pre-auto-gc
	~~~~~~~~~~~

	This hook is invoked by 'git gc --auto'. It takes no parameter, and
	exiting with non-zero status from this script causes the 'git gc --auto'
	to abort.

	post-rewrite
	~~~~~~~~~~~~

	This hook is invoked by commands that rewrite commits (`git commit
	--amend`, 'git-rebase'; currently 'git-filter-branch' does 'not' call
	it!). Its first argument denotes the command it was invoked by:
	currently one of `amend` or `rebase`. Further command-dependent
	arguments may be passed in the future.

	The hook receives a list of the rewritten commits on stdin, in the
	format

	<old-sha1> SP <new-sha1> [ SP <extra-info> ] LF

	The 'extra-info' is again command-dependent. If it is empty, the
	preceding SP is also omitted. Currently, no commands pass any
	'extra-info'.

	The hook always runs after the automatic note copying (see
	"notes.rewrite.<command>" in linkgit:git-config[1]) has happened, and
	thus has access to these notes.

	The following command-specific comments apply:

	rebase::
	For the 'squash' and 'fixup' operation, all commits that were
	squashed are listed as being rewritten to the squashed commit.
	This means that there will be several lines sharing the same
	'new-sha1'.
	+
	The commits are guaranteed to be listed in the order that they were
	processed by rebase.

	sendemail-validate
	~~~~~~~~~~~~~~~~~~

	This hook is invoked by 'git send-email'. It takes a single parameter,
	the name of the file that holds the e-mail to be sent. Exiting with a
	non-zero status causes 'git send-email' to abort before sending any
	e-mails.


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