When you run a Mercurial command in a repository, and the command causes a hook to run, that hook runs on your system, under your user account, with your privilege level. Since hooks are arbitrary pieces of executable code, you should treat them with an appropriate level of suspicion. Do not install a hook unless you are confident that you know who created it and what it does.

In some cases, you may be exposed to hooks that you did not install yourself. If you work with Mercurial on an unfamiliar system, Mercurial will run hooks defined in that system's global ~/.hgrc file.

If you are working with a repository owned by another user, Mercurial can run hooks defined in that user's repository, but it will still run them as “you”. For example, if you hg pull from that repository, and its .hg/hgrc defines a local outgoing hook, that hook will run under your user account, even though you don't own that repository.

	Note
	This only applies if you are pulling from a repository on a local or network filesystem. If you're pulling over http or ssh, any outgoing hook will run under whatever account is executing the server process, on the server.

To see what hooks are defined in a repository, use the hg showconfig hooks command. If you are working in one repository, but talking to another that you do not own (e.g. using hg pull or hg incoming), remember that it is the other repository's hooks you should be checking, not your own.

In Mercurial, hooks are not revision controlled, and do not propagate when you clone, or pull from, a repository. The reason for this is simple: a hook is a completely arbitrary piece of executable code. It runs under your user identity, with your privilege level, on your machine.

It would be extremely reckless for any distributed revision control system to implement revision-controlled hooks, as this would offer an easily exploitable way to subvert the accounts of users of the revision control system.

Since Mercurial does not propagate hooks, if you are collaborating with other people on a common project, you should not assume that they are using the same Mercurial hooks as you are, or that theirs are correctly configured. You should document the hooks you expect people to use.

In a corporate intranet, this is somewhat easier to control, as you can for example provide a “standard” installation of Mercurial on an NFS filesystem, and use a site-wide ~/.hgrc file to define hooks that all users will see. However, this too has its limits; see below.

Mercurial allows you to override a hook definition by redefining the hook. You can disable it by setting its value to the empty string, or change its behavior as you wish.

If you deploy a system- or site-wide ~/.hgrc file that defines some hooks, you should thus understand that your users can disable or override those hooks.

Sometimes you may want to enforce a policy that you do not want others to be able to work around. For example, you may have a requirement that every changeset must pass a rigorous set of tests. Defining this requirement via a hook in a site-wide ~/.hgrc won't work for remote users on laptops, and of course local users can subvert it at will by overriding the hook.

Instead, you can set up your policies for use of Mercurial so that people are expected to propagate changes through a well-known “canonical” server that you have locked down and configured appropriately.

One way to do this is via a combination of social engineering and technology. Set up a restricted-access account; users can push changes over the network to repositories managed by this account, but they cannot log into the account and run normal shell commands. In this scenario, a user can commit a changeset that contains any old garbage they want.

When someone pushes a changeset to the server that everyone pulls from, the server will test the changeset before it accepts it as permanent, and reject it if it fails to pass the test suite. If people only pull changes from this filtering server, it will serve to ensure that all changes that people pull have been automatically vetted.

Quite often, you will want to define more than one hook for a particular kind of event, as shown below.

$ echo 'commit.when = echo -n "date of commit: "; date' >> .hg/hgrc
$ echo a >> a
$ hg commit -m 'i have two hooks'
committed 669d3ac83eae08ced498b61829441d922eb5cf1d
date of commit: Tue May  5 06:55:36 GMT 2009

Mercurial lets you do this by adding an extension to the end of a hook's name. You extend a hook's name by giving the name of the hook, followed by a full stop (the “.” character), followed by some more text of your choosing. For example, Mercurial will run both commit.foo and commit.bar when the commit event occurs.

To give a well-defined order of execution when there are multiple hooks defined for an event, Mercurial sorts hooks by extension, and executes the hook commands in this sorted order. In the above example, it will execute commit.bar before commit.foo, and commit before both.

It is a good idea to use a somewhat descriptive extension when you define a new hook. This will help you to remember what the hook was for. If the hook fails, you'll get an error message that contains the hook name and extension, so using a descriptive extension could give you an immediate hint as to why the hook failed (see the section called “Controlling whether an activity can proceed” for an example).

In our earlier examples, we used the commit hook, which is run after a commit has completed. This is one of several Mercurial hooks that run after an activity finishes. Such hooks have no way of influencing the activity itself.

Mercurial defines a number of events that occur before an activity starts; or after it starts, but before it finishes. Hooks that trigger on these events have the added ability to choose whether the activity can continue, or will abort.

The pretxncommit hook runs after a commit has all but completed. In other words, the metadata representing the changeset has been written out to disk, but the transaction has not yet been allowed to complete. The pretxncommit hook has the ability to decide whether the transaction can complete, or must be rolled back.

If the pretxncommit hook exits with a status code of zero, the transaction is allowed to complete; the commit finishes; and the commit hook is run. If the pretxncommit hook exits with a non-zero status code, the transaction is rolled back; the metadata representing the changeset is erased; and the commit hook is not run.

$ cat check_bug_id
#!/bin/sh
# check that a commit comment mentions a numeric bug id
hg log -r $1 --template {desc} | grep -q "\<bug *[0-9]"
$ echo 'pretxncommit.bug_id_required = ./check_bug_id $HG_NODE' >> .hg/hgrc
$ echo a >> a
$ hg commit -m 'i am not mentioning a bug id'
transaction abort!
rollback completed
abort: pretxncommit.bug_id_required hook exited with status 1
$ hg commit -m 'i refer you to bug 666'
committed 052ec7f13869f36df5932e83e2a24164d8040aab
date of commit: Tue May  5 06:55:36 GMT 2009

The hook in the example above checks that a commit comment contains a bug ID. If it does, the commit can complete. If not, the commit is rolled back.

You can write a hook either as a normal program—typically a shell script—or as a Python function that is executed within the Mercurial process.

Writing a hook as an external program has the advantage that it requires no knowledge of Mercurial's internals. You can call normal Mercurial commands to get any added information you need. The trade-off is that external hooks are slower than in-process hooks.

An in-process Python hook has complete access to the Mercurial API, and does not “shell out” to another process, so it is inherently faster than an external hook. It is also easier to obtain much of the information that a hook requires by using the Mercurial API than by running Mercurial commands.

If you are comfortable with Python, or require high performance, writing your hooks in Python may be a good choice. However, when you have a straightforward hook to write and you don't need to care about performance (probably the majority of hooks), a shell script is perfectly fine.

Mercurial calls each hook with a set of well-defined parameters. In Python, a parameter is passed as a keyword argument to your hook function. For an external program, a parameter is passed as an environment variable.

Whether your hook is written in Python or as a shell script, the hook-specific parameter names and values will be the same. A boolean parameter will be represented as a boolean value in Python, but as the number 1 (for “true”) or 0 (for “false”) as an environment variable for an external hook. If a hook parameter is named foo, the keyword argument for a Python hook will also be named foo, while the environment variable for an external hook will be named HG_FOO.

A hook that executes successfully must exit with a status of zero if external, or return boolean “false” if in-process. Failure is indicated with a non-zero exit status from an external hook, or an in-process hook returning boolean “true”. If an in-process hook raises an exception, the hook is considered to have failed.

For a hook that controls whether an activity can proceed, zero/false means “allow”, while non-zero/true/exception means “deny”.

When you define an external hook in your ~/.hgrc and the hook is run, its value is passed to your shell, which interprets it. This means that you can use normal shell constructs in the body of the hook.

An executable hook is always run with its current directory set to a repository's root directory.

Each hook parameter is passed in as an environment variable; the name is upper-cased, and prefixed with the string “HG_”.

With the exception of hook parameters, Mercurial does not set or modify any environment variables when running a hook. This is useful to remember if you are writing a site-wide hook that may be run by a number of different users with differing environment variables set. In multi-user situations, you should not rely on environment variables being set to the values you have in your environment when testing the hook.

The ~/.hgrc syntax for defining an in-process hook is slightly different than for an executable hook. The value of the hook must start with the text “python:”, and continue with the fully-qualified name of a callable object to use as the hook's value.

The module in which a hook lives is automatically imported when a hook is run. So long as you have the module name and PYTHONPATH right, it should “just work”.

The following ~/.hgrc example snippet illustrates the syntax and meaning of the notions we just described.

[hooks]
commit.example = python:mymodule.submodule.myhook

When Mercurial runs the commit.example hook, it imports mymodule.submodule, looks for the callable object named myhook, and calls it.

The simplest in-process hook does nothing, but illustrates the basic shape of the hook API:

def myhook(ui, repo, **kwargs):
    pass

The first argument to a Python hook is always a ui object. The second is a repository object; at the moment, it is always an instance of localrepository. Following these two arguments are other keyword arguments. Which ones are passed in depends on the hook being called, but a hook can ignore arguments it doesn't care about by dropping them into a keyword argument dict, as with **kwargs above.

It's hard to imagine a useful commit message being very short. The simple pretxncommit hook of the example below will prevent you from committing a changeset with a message that is less than ten bytes long.

$ cat .hg/hgrc
[hooks]
pretxncommit.msglen = test `hg tip --template {desc} | wc -c` -ge 10
$ echo a > a
$ hg add a
$ hg commit -A -m 'too short'
transaction abort!
rollback completed
abort: pretxncommit.msglen hook exited with status 1
$ hg commit -A -m 'long enough'

An interesting use of a commit-related hook is to help you to write cleaner code. A simple example of “cleaner code” is the dictum that a change should not add any new lines of text that contain “trailing whitespace”. Trailing whitespace is a series of space and tab characters at the end of a line of text. In most cases, trailing whitespace is unnecessary, invisible noise, but it is occasionally problematic, and people often prefer to get rid of it.

You can use either the precommit or pretxncommit hook to tell whether you have a trailing whitespace problem. If you use the precommit hook, the hook will not know which files you are committing, so it will have to check every modified file in the repository for trailing white space. If you want to commit a change to just the file foo, but the file bar contains trailing whitespace, doing a check in the precommit hook will prevent you from committing foo due to the problem with bar. This doesn't seem right.

Should you choose the pretxncommit hook, the check won't occur until just before the transaction for the commit completes. This will allow you to check for problems only the exact files that are being committed. However, if you entered the commit message interactively and the hook fails, the transaction will roll back; you'll have to re-enter the commit message after you fix the trailing whitespace and run hg commit again.

$ cat .hg/hgrc
[hooks]
pretxncommit.whitespace = hg export tip | (! egrep -q '^\+.*[ \t]$')
$ echo 'a ' > a
$ hg commit -A -m 'test with trailing whitespace'
adding a
transaction abort!
rollback completed
abort: pretxncommit.whitespace hook exited with status 1
$ echo 'a' > a
$ hg commit -A -m 'drop trailing whitespace and try again'

In this example, we introduce a simple pretxncommit hook that checks for trailing whitespace. This hook is short, but not very helpful. It exits with an error status if a change adds a line with trailing whitespace to any file, but does not print any information that might help us to identify the offending file or line. It also has the nice property of not paying attention to unmodified lines; only lines that introduce new trailing whitespace cause problems.

#!/usr/bin/env python
#
# save as .hg/check_whitespace.py and make executable

import re

def trailing_whitespace(difflines):
    # 
    linenum, header = 0, False

    for line in difflines:
        if header:
            # remember the name of the file that this diff affects
            m = re.match(r'(?:---|\+\+\+) ([^\t]+)', line)
            if m and m.group(1) != '/dev/null':
                filename = m.group(1).split('/', 1)[-1]
            if line.startswith('+++ '):
                header = False
            continue
        if line.startswith('diff '):
            header = True
            continue
        # hunk header - save the line number
        m = re.match(r'@@ -\d+,\d+ \+(\d+),', line)
        if m:
            linenum = int(m.group(1))
            continue
        # hunk body - check for an added line with trailing whitespace
        m = re.match(r'\+.*\s$', line)
        if m:
            yield filename, linenum
        if line and line[0] in ' +':
            linenum += 1

if __name__ == '__main__':
    import os, sys
    
    added = 0
    for filename, linenum in trailing_whitespace(os.popen('hg export tip')):
        print >> sys.stderr, ('%s, line %d: trailing whitespace added' %
                              (filename, linenum))
        added += 1
    if added:
        # save the commit message so we don't need to retype it
        os.system('hg tip --template "{desc}" > .hg/commit.save')
        print >> sys.stderr, 'commit message saved to .hg/commit.save'
        sys.exit(1)

The above version is much more complex, but also more useful. It parses a unified diff to see if any lines add trailing whitespace, and prints the name of the file and the line number of each such occurrence. Even better, if the change adds trailing whitespace, this hook saves the commit comment and prints the name of the save file before exiting and telling Mercurial to roll the transaction back, so you can use the -l filename option to hg commit to reuse the saved commit message once you've corrected the problem.

$ cat .hg/hgrc
[hooks]
pretxncommit.whitespace = .hg/check_whitespace.py
$ echo 'a ' >> a
$ hg commit -A -m 'add new line with trailing whitespace'
a, line 2: trailing whitespace added
commit message saved to .hg/commit.save
transaction abort!
rollback completed
abort: pretxncommit.whitespace hook exited with status 1
$ sed -i 's, *$,,' a
$ hg commit -A -m 'trimmed trailing whitespace'
a, line 2: trailing whitespace added
commit message saved to .hg/commit.save
transaction abort!
rollback completed
abort: pretxncommit.whitespace hook exited with status 1

As a final aside, note in the example above the use of sed's in-place editing feature to get rid of trailing whitespace from a file. This is concise and useful enough that I will reproduce it here (using perl for good measure).

perl -pi -e 's,\s+$,,' filename

The acl extension lets you control which remote users are allowed to push changesets to a networked server. You can protect any portion of a repository (including the entire repo), so that a specific remote user can push changes that do not affect the protected portion.

This extension implements access control based on the identity of the user performing a push, not on who committed the changesets they're pushing. It makes sense to use this hook only if you have a locked-down server environment that authenticates remote users, and you want to be sure that only specific users are allowed to push changes to that server.

[hooks]
pretxnchangegroup.acl = python:hgext.acl.hook

[acl.allow]
docs/** = docwriter
[acl.deny]
source/sensitive/** = intern

[ui]
debug = true

The bugzilla extension adds a comment to a Bugzilla bug whenever it finds a reference to that bug ID in a commit comment. You can install this hook on a shared server, so that any time a remote user pushes changes to this server, the hook gets run.

It adds a comment to the bug that looks like this (you can configure the contents of the comment—see below):

Changeset aad8b264143a, made by Joe User
	<joe.user@domain.com> in the frobnitz repository, refers
	to this bug. For complete details, see
	http://hg.domain.com/frobnitz?cmd=changeset;node=aad8b264143a
	Changeset description: Fix bug 10483 by guarding against some
	NULL pointers

The value of this hook is that it automates the process of updating a bug any time a changeset refers to it. If you configure the hook properly, it makes it easy for people to browse straight from a Bugzilla bug to a changeset that refers to that bug.

You can use the code in this hook as a starting point for some more exotic Bugzilla integration recipes. Here are a few possibilities:

[hooks]
incoming.bugzilla = python:hgext.bugzilla.hook

[usermap]
jane.user@example.com = jane

# regular hgrc file refers to external usermap file
[bugzilla]
usermap = /home/hg/repos/userdata/bugzilla-usermap.conf

# bugzilla-usermap.conf - inside a hg repository
[usermap] stephanie@example.com = steph

[web]
baseurl = http://hg.domain.com/

[bugzilla]
host = bugzilla.example.com
password = mypassword version = 2.16
# server-side repos live in /home/hg/repos, so strip 4 leading
# separators
strip = 4
hgweb = http://hg.example.com/
usermap = /home/hg/repos/notify/bugzilla.conf
template = Changeset {node|short}, made by {author} in the {webroot}
  repo, refers to this bug.\n
  For complete details, see
  {hgweb}{webroot}?cmd=changeset;node={node|short}\n
  Changeset description:\n
  \t{desc|tabindent}

hg_user = (httpd_user)
NOPASSWD: /var/www/html/bugzilla/processmail-wrapper %s

#!/bin/sh
cd `dirname $0` && ./processmail "$1" nobody@example.com

cannot find bugzilla user id for john.q.public@example.com

Although Mercurial's built-in web server provides RSS feeds of changes in every repository, many people prefer to receive change notifications via email. The notify hook lets you send out notifications to a set of email addresses whenever changesets arrive that those subscribers are interested in.

As with the bugzilla hook, the notify hook is template-driven, so you can customise the contents of the notification messages that it sends.

By default, the notify hook includes a diff of every changeset that it sends out; you can limit the size of the diff, or turn this feature off entirely. It is useful for letting subscribers review changes immediately, rather than clicking to follow a URL.

[hooks]
# send one email per group of changes
changegroup.notify = python:hgext.notify.hook
# send one email per change
incoming.notify = python:hgext.notify.hook

[notify]
# really send email
test = false
# subscriber data lives in the notify repo
config = /home/hg/repos/notify/notify.conf
# repos live in /home/hg/repos on server, so strip 4 "/" chars
strip = 4
template = X-Hg-Repo: {webroot}\n
  Subject: {webroot}: {desc|firstline|strip}\n
  From: {author}
  \n\n
  changeset {node|short} in {root}
  \n\ndetails:
  {baseurl}{webroot}?cmd=changeset;node={node|short}
  description: {desc|tabindent|strip}

[web]
baseurl =
http://hg.example.com/

X-Hg-Repo: tests/slave
Subject: tests/slave: Handle error case when slave has no buffers
Date: Wed,  2 Aug 2006 15:25:46 -0700 (PDT)

changeset 3cba9bfe74b5 in /home/hg/repos/tests/slave

details:
http://hg.example.com/tests/slave?cmd=changeset;node=3cba9bfe74b5 

description: Handle error case when slave has no buffers

diffs (54 lines):
diff -r 9d95df7cf2ad -r 3cba9bfe74b5 include/tests.h
--- a/include/tests.h      Wed Aug 02 15:19:52 2006 -0700
+++ b/include/tests.h      Wed Aug 02 15:25:26 2006 -0700
@@ -212,6 +212,15 @@ static __inline__
void test_headers(void *h)
[...snip...]

An in-process hook is called with arguments of the following form:

def myhook(ui, repo, **kwargs): pass

The ui parameter is a ui object. The repo parameter is a localrepository object. The names and values of the **kwargs parameters depend on the hook being invoked, with the following common features:

An in-process hook is called without a change to the process's working directory (unlike external hooks, which are run in the root of the repository). It must not change the process's working directory, or it will cause any calls it makes into the Mercurial API to fail.

If a hook returns a boolean “false” value, it is considered to have succeeded. If it returns a boolean “true” value or raises an exception, it is considered to have failed. A useful way to think of the calling convention is “tell me if you fail”.

Note that changeset IDs are passed into Python hooks as hexadecimal strings, not the binary hashes that Mercurial's APIs normally use. To convert a hash from hex to binary, use the bin function.

An external hook is passed to the shell of the user running Mercurial. Features of that shell, such as variable substitution and command redirection, are available. The hook is run in the root directory of the repository (unlike in-process hooks, which are run in the same directory that Mercurial was run in).

Hook parameters are passed to the hook as environment variables. Each environment variable's name is converted in upper case and prefixed with the string “HG_”. For example, if the name of a parameter is “node”, the name of the environment variable representing that parameter will be “HG_NODE”.

A boolean parameter is represented as the string “1” for “true”, “0” for “false”. If an environment variable is named HG_NODE, HG_PARENT1 or HG_PARENT2, it contains a changeset ID represented as a hexadecimal string. The empty string is used to represent “null changeset ID” instead of a string of zeroes. If an environment variable is named HG_URL, it will contain the URL of a remote repository, if that can be determined.

If a hook exits with a status of zero, it is considered to have succeeded. If it exits with a non-zero status, it is considered to have failed.

A hook that involves the transfer of changesets between a local repository and another may be able to find out information about the “far side”. Mercurial knows how changes are being transferred, and in many cases where they are being transferred to or from.

This hook is run after a group of pre-existing changesets has been added to the repository, for example via a hg pull or hg unbundle. This hook is run once per operation that added one or more changesets. This is in contrast to the incoming hook, which is run once per changeset, regardless of whether the changesets arrive in a group.

Some possible uses for this hook include kicking off an automated build or test of the added changesets, updating a bug database, or notifying subscribers that a repository contains new changes.

Parameters to this hook:

See also: incoming (the section called “incoming—after one remote changeset is added”), prechangegroup (the section called “prechangegroup—before starting to add remote changesets”), pretxnchangegroup (the section called “pretxnchangegroup—before completing addition of remote changesets”)

This hook is run after a new changeset has been created.

Parameters to this hook:

See also: precommit (the section called “precommit—before starting to commit a changeset”), pretxncommit (the section called “pretxncommit—before completing commit of new changeset”)

This hook is run after a pre-existing changeset has been added to the repository, for example via a hg push. If a group of changesets was added in a single operation, this hook is called once for each added changeset.

You can use this hook for the same purposes as the changegroup hook (the section called “changegroup—after remote changesets added”); it's simply more convenient sometimes to run a hook once per group of changesets, while other times it's handier once per changeset.

Parameters to this hook:

See also: changegroup (the section called “changegroup—after remote changesets added”) prechangegroup (the section called “prechangegroup—before starting to add remote changesets”), pretxnchangegroup (the section called “pretxnchangegroup—before completing addition of remote changesets”)

This hook is run after a group of changesets has been propagated out of this repository, for example by a hg push or hg bundle command.

One possible use for this hook is to notify administrators that changes have been pulled.

Parameters to this hook:

See also: preoutgoing (the section called “preoutgoing—before starting to propagate changesets”)

This controlling hook is run before Mercurial begins to add a group of changesets from another repository.

This hook does not have any information about the changesets to be added, because it is run before transmission of those changesets is allowed to begin. If this hook fails, the changesets will not be transmitted.

One use for this hook is to prevent external changes from being added to a repository. For example, you could use this to “freeze” a server-hosted branch temporarily or permanently so that users cannot push to it, while still allowing a local administrator to modify the repository.

Parameters to this hook:

See also: changegroup (the section called “changegroup—after remote changesets added”), incoming (the section called “incoming—after one remote changeset is added”), pretxnchangegroup (the section called “pretxnchangegroup—before completing addition of remote changesets”)

This hook is run before Mercurial begins to commit a new changeset. It is run before Mercurial has any of the metadata for the commit, such as the files to be committed, the commit message, or the commit date.

One use for this hook is to disable the ability to commit new changesets, while still allowing incoming changesets. Another is to run a build or test, and only allow the commit to begin if the build or test succeeds.

Parameters to this hook:

If the commit proceeds, the parents of the working directory will become the parents of the new changeset.

See also: commit (the section called “commit—after a new changeset is created”), pretxncommit (the section called “pretxncommit—before completing commit of new changeset”)

This hook is invoked before Mercurial knows the identities of the changesets to be transmitted.

One use for this hook is to prevent changes from being transmitted to another repository.

Parameters to this hook:

See also: outgoing (the section called “outgoing—after changesets are propagated”)

This controlling hook is run before a tag is created. If the hook succeeds, creation of the tag proceeds. If the hook fails, the tag is not created.

Parameters to this hook:

If the tag to be created is revision-controlled, the precommit and pretxncommit hooks (the section called “commit—after a new changeset is created” and the section called “pretxncommit—before completing commit of new changeset”) will also be run.

See also: tag (the section called “tag—after tagging a changeset”)

This controlling hook is run before a transaction—that manages the addition of a group of new changesets from outside the repository—completes. If the hook succeeds, the transaction completes, and all of the changesets become permanent within this repository. If the hook fails, the transaction is rolled back, and the data for the changesets is erased.

This hook can access the metadata associated with the almost-added changesets, but it should not do anything permanent with this data. It must also not modify the working directory.

While this hook is running, if other Mercurial processes access this repository, they will be able to see the almost-added changesets as if they are permanent. This may lead to race conditions if you do not take steps to avoid them.

This hook can be used to automatically vet a group of changesets. If the hook fails, all of the changesets are “rejected” when the transaction rolls back.

Parameters to this hook:

See also: changegroup (the section called “changegroup—after remote changesets added”), incoming (the section called “incoming—after one remote changeset is added”), prechangegroup (the section called “prechangegroup—before starting to add remote changesets”)

This controlling hook is run before a transaction—that manages a new commit—completes. If the hook succeeds, the transaction completes and the changeset becomes permanent within this repository. If the hook fails, the transaction is rolled back, and the commit data is erased.

This hook can access the metadata associated with the almost-new changeset, but it should not do anything permanent with this data. It must also not modify the working directory.

While this hook is running, if other Mercurial processes access this repository, they will be able to see the almost-new changeset as if it is permanent. This may lead to race conditions if you do not take steps to avoid them.

Parameters to this hook:

See also: precommit (the section called “precommit—before starting to commit a changeset”)

This controlling hook is run before an update or merge of the working directory begins. It is run only if Mercurial's normal pre-update checks determine that the update or merge can proceed. If the hook succeeds, the update or merge may proceed; if it fails, the update or merge does not start.

Parameters to this hook:

See also: update (the section called “update—after updating or merging working directory”)

This hook is run after a tag has been created.

Parameters to this hook:

If the created tag is revision-controlled, the commit hook (section the section called “commit—after a new changeset is created”) is run before this hook.

See also: pretag (the section called “pretag—before tagging a changeset”)

This hook is run after an update or merge of the working directory completes. Since a merge can fail (if the external hgmerge command fails to resolve conflicts in a file), this hook communicates whether the update or merge completed cleanly.

See also: preupdate (the section called “preupdate—before updating or merging working directory”)