hgbook
view en/hook.tex @ 54:e94202d88199
Tix fypos.
| author | Bryan O'Sullivan <bos@serpentine.com> |
|---|---|
| date | Wed Aug 02 13:08:56 2006 -0700 (2006-08-02) |
| parents | 497aa3c9d4ce |
| children | 8806b2875f10 |
line source
1 \chapter{Handling repository events with hooks}
2 \label{chap:hook}
4 Mercurial offers a powerful mechanism to let you perform automated
5 actions in response to events that occur in a repository. In some
6 cases, you can even control Mercurial's response to those events.
8 The name Mercurial uses for one of these actions is a \emph{hook}.
9 Hooks are called ``triggers'' in some revision control systems, but
10 the two names refer to the same idea.
12 \section{An overview of hooks in Mercurial}
14 Here is a brief list of the hooks that Mercurial supports. We will
15 revisit each of these hooks in more detail later, in
16 section~\ref{sec:hook:ref}.
18 \begin{itemize}
19 \item[\small\hook{changegroup}] This is run after a group of
20 changesets has been brought into the repository from elsewhere.
21 \item[\small\hook{commit}] This is run after a new changeset has been
22 created in the local repository.
23 \item[\small\hook{incoming}] This is run once for each new changeset
24 that is brought into the repository from elsewhere. Notice the
25 difference from \hook{changegroup}, which is run once per
26 \emph{group} of changesets brought in.
27 \item[\small\hook{outgoing}] This is run after a group of changesets
28 has been transmitted from this repository.
29 \item[\small\hook{prechangegroup}] This is run before starting to
30 bring a group of changesets into the repository.
31 \item[\small\hook{precommit}] Controlling. This is run before starting
32 a commit.
33 \item[\small\hook{preoutgoing}] Controlling. This is run before
34 starting to transmit a group of changesets from this repository.
35 \item[\small\hook{pretag}] Controlling. This is run before creating a tag.
36 \item[\small\hook{pretxnchangegroup}] Controlling. This is run after a
37 group of changesets has been brought into the local repository from
38 another, but before the transaction completes that will make the
39 changes permanent in the repository.
40 \item[\small\hook{pretxncommit}] Controlling. This is run after a new
41 changeset has been created in the local repository, but before the
42 transaction completes that will make it permanent.
43 \item[\small\hook{preupdate}] Controlling. This is run before starting
44 an update or merge of the working directory.
45 \item[\small\hook{tag}] This is run after a tag is created.
46 \item[\small\hook{update}] This is run after an update or merge of the
47 working directory has finished.
48 \end{itemize}
49 Each of the hooks whose description begins with the word
50 ``Controlling'' has the ability to determine whether an activity can
51 proceed. If the hook succeeds, the activity may proceed; if it fails,
52 the activity is either not permitted or undone, depending on the hook.
54 \section{Hooks and security}
56 \subsection{Hooks are run with your privileges}
58 When you run a Mercurial command in a repository, and the command
59 causes a hook to run, that hook runs on \emph{your} system, under
60 \emph{your} user account, with \emph{your} privilege level. Since
61 hooks are arbitrary pieces of executable code, you should treat them
62 with an appropriate level of suspicion. Do not install a hook unless
63 you are confident that you know who created it and what it does.
65 In some cases, you may be exposed to hooks that you did not install
66 yourself. If you work with Mercurial on an unfamiliar system,
67 Mercurial will run hooks defined in that system's global \hgrc\ file.
69 If you are working with a repository owned by another user, Mercurial
70 can run hooks defined in that user's repository, but it will still run
71 them as ``you''. For example, if you \hgcmd{pull} from that
72 repository, and its \sfilename{.hg/hgrc} defines a local
73 \hook{outgoing} hook, that hook will run under your user account, even
74 though you don't own that repository.
76 \begin{note}
77 This only applies if you are pulling from a repository on a local or
78 network filesystem. If you're pulling over http or ssh, any
79 \hook{outgoing} hook will run under whatever account is executing
80 the server process, on the server.
81 \end{note}
83 XXX To see what hooks are defined in a repository, use the
84 \hgcmdargs{config}{hooks} command. If you are working in one
85 repository, but talking to another that you do not own (e.g.~using
86 \hgcmd{pull} or \hgcmd{incoming}), remember that it is the other
87 repository's hooks you should be checking, not your own.
89 \subsection{Hooks do not propagate}
91 In Mercurial, hooks are not revision controlled, and do not propagate
92 when you clone, or pull from, a repository. The reason for this is
93 simple: a hook is a completely arbitrary piece of executable code. It
94 runs under your user identity, with your privilege level, on your
95 machine.
97 It would be extremely reckless for any distributed revision control
98 system to implement revision-controlled hooks, as this would offer an
99 easily exploitable way to subvert the accounts of users of the
100 revision control system.
102 Since Mercurial does not propagate hooks, if you are collaborating
103 with other people on a common project, you should not assume that they
104 are using the same Mercurial hooks as you are, or that theirs are
105 correctly configured. You should document the hooks you expect people
106 to use.
108 In a corporate intranet, this is somewhat easier to control, as you
109 can for example provide a ``standard'' installation of Mercurial on an
110 NFS filesystem, and use a site-wide \hgrc\ file to define hooks that
111 all users will see. However, this too has its limits; see below.
113 \subsection{Hooks can be overridden}
115 Mercurial allows you to override a hook definition by redefining the
116 hook. You can disable it by setting its value to the empty string, or
117 change its behaviour as you wish.
119 If you deploy a system-~or site-wide \hgrc\ file that defines some
120 hooks, you should thus understand that your users can disable or
121 override those hooks.
123 \subsection{Ensuring that critical hooks are run}
125 Sometimes you may want to enforce a policy that you do not want others
126 to be able to work around. For example, you may have a requirement
127 that every changeset must pass a rigorous set of tests. Defining this
128 requirement via a hook in a site-wide \hgrc\ won't work for remote
129 users on laptops, and of course local users can subvert it at will by
130 overriding the hook.
132 Instead, you can set up your policies for use of Mercurial so that
133 people are expected to propagate changes through a well-known
134 ``canonical'' server that you have locked down and configured
135 appropriately.
137 One way to do this is via a combination of social engineering and
138 technology. Set up a restricted-access account; users can push
139 changes over the network to repositories managed by this account, but
140 they cannot log into the account and run normal shell commands. In
141 this scenario, a user can commit a changeset that contains any old
142 garbage they want.
144 When someone pushes a changeset to the server that everyone pulls
145 from, the server will test the changeset before it accepts it as
146 permanent, and reject it if it fails to pass the test suite. If
147 people only pull changes from this filtering server, it will serve to
148 ensure that all changes that people pull have been automatically
149 vetted.
151 \section{Using hooks with shared access to a repository}
153 If you want to use hooks to so some automated work in a repository
154 that a number of people have shared access to, you need to be careful
155 in how you do this.
157 Mercurial only locks a repository when it is writing to the
158 repository, and only the parts of Mercurial that write to the
159 repository pay attention to locks. Write locks are necessary to
160 prevent multiple simultaneous writers from scribbling on each other's
161 work, corrupting the repository.
163 Because Mercurial is careful with the order in which it reads and
164 writes data, it does not need to acquire a lock when it wants to read
165 data from the repository. The parts of Mercurial that read from the
166 repository never pay attention to locks. This lockless reading scheme
167 greatly increases performance and concurrency.
169 With great performance comes a trade-off, though, one which has the
170 potential to cause you trouble unless you're aware of it. To describe
171 this requires a little detail about how Mercurial adds changesets to a
172 repository and reads those changes.
174 When Mercurial \emph{writes} metadata, it writes it straight into the
175 destination file. It writes file data first, then manifest data
176 (which contains pointers to the new file data), then changelog data
177 (which contains pointers to the new manifest data). Before the first
178 write to each file, it stores a record of where the end of the file
179 was in its transaction log. If the transaction must be rolled back,
180 Mercurial simply truncates each file back to the size it was before the
181 transaction began.
183 When Mercurial \emph{reads} metadata, it reads the changelog first,
184 then everything else. Since a reader will only access parts of the
185 manifest or file metadata that it can see in the changelog, it can
186 never see partially written data.
188 Some controlling hooks (\hook{pretxncommit} and
189 \hook{pretxnchangegroup}) run when a transaction is almost complete.
190 All of the metadata has been written, but Mercurial can still roll the
191 transaction back and cause the newly-written data to disappear.
193 If one of these hooks runs for long, it opens a window in which a
194 reader can see the metadata for changesets that are, strictly
195 speaking, not yet permanent. The longer the hook runs, the bigger the
196 window.
198 A good use for the \hook{pretxnchangegroup} hook would be to
199 automatically build and test incoming changes before they are accepted
200 into the repository, so that you can guarantee that nobody can push
201 changes to this repository that ``break the build''. But if a client
202 can pull changes while they're being tested, the usefulness of the
203 test is zero; someone can pull untested changes.
205 The safest answer to this challenge is to set up such a ``gatekeeper''
206 repository as \emph{unidirectional}. It can take changes pushed in
207 from the outside, but nobody can pull changes from it. Use the
208 \hook{preoutgoing} hook to lock it down. Configure a
209 \hook{changegroup} hook so that if a build or test succeeds, the hook
210 will push the new changes out to another repository that people
211 \emph{can} pull from.
213 \section{A short tutorial on using hooks}
214 \label{sec:hook:simple}
216 It is easy to write a Mercurial hook. Let's start with a hook that
217 runs when you finish a \hgcmd{commit}, and simply prints the hash of
218 the changeset you just created. The hook is called \hook{commit}.
220 \begin{figure}[ht]
221 \interaction{hook.simple.init}
222 \caption{A simple hook that runs when a changeset is committed}
223 \label{ex:hook:init}
224 \end{figure}
226 All hooks follow the pattern in example~\ref{ex:hook:init}. You add
227 an entry to the \rcsection{hooks} section of your \hgrc\. On the left
228 is the name of the event to trigger on; on the right is the action to
229 take. As you can see, you can run an arbitrary shell command in a
230 hook. Mercurial passes extra information to the hook using
231 environment variables (look for \envar{HG\_NODE} in the example).
233 \subsection{Performing multiple actions per event}
235 Quite often, you will want to define more than one hook for a
236 particular kind of event, as shown in example~\ref{ex:hook:ext}.
237 Mercurial lets you do this by adding an \emph{extension} to the end of
238 a hook's name. You extend a hook's name by giving the name of the
239 hook, followed by a full stop (the ``\texttt{.}'' character), followed
240 by some more text of your choosing. For example, Mercurial will run
241 both \texttt{commit.foo} and \texttt{commit.bar} when the
242 \texttt{commit} event occurs.
244 \begin{figure}[ht]
245 \interaction{hook.simple.ext}
246 \caption{Defining a second \hook{commit} hook}
247 \label{ex:hook:ext}
248 \end{figure}
250 To give a well-defined order of execution when there are multiple
251 hooks defined for an event, Mercurial sorts hooks by extension, and
252 executes the hook commands in this sorted order. In the above
253 example, it will execute \texttt{commit.bar} before
254 \texttt{commit.foo}, and \texttt{commit} before both.
256 It is a good idea to use a somewhat descriptive extension when you
257 define a new hook. This will help you to remember what the hook was
258 for. If the hook fails, you'll get an error message that contains the
259 hook name and extension, so using a descriptive extension could give
260 you an immediate hint as to why the hook failed (see
261 section~\ref{sec:hook:perm} for an example).
263 \subsection{Controlling whether an activity can proceed}
264 \label{sec:hook:perm}
266 In our earlier examples, we used the \hook{commit} hook, which is
267 run after a commit has completed. This is one of several Mercurial
268 hooks that run after an activity finishes. Such hooks have no way of
269 influencing the activity itself.
271 Mercurial defines a number of events that occur before an activity
272 starts; or after it starts, but before it finishes. Hooks that
273 trigger on these events have the added ability to choose whether the
274 activity can continue, or will abort.
276 The \hook{pretxncommit} hook runs after a commit has all but
277 completed. In other words, the metadata representing the changeset
278 has been written out to disk, but the transaction has not yet been
279 allowed to complete. The \hook{pretxncommit} hook has the ability to
280 decide whether the transaction can complete, or must be rolled back.
282 If the \hook{pretxncommit} hook exits with a status code of zero, the
283 transaction is allowed to complete; the commit finishes; and the
284 \hook{commit} hook is run. If the \hook{pretxncommit} hook exits with
285 a non-zero status code, the transaction is rolled back; the metadata
286 representing the changeset is erased; and the \hook{commit} hook is
287 not run.
289 \begin{figure}[ht]
290 \interaction{hook.simple.pretxncommit}
291 \caption{Using the \hook{pretxncommit} hook to control commits}
292 \label{ex:hook:pretxncommit}
293 \end{figure}
295 The hook in example~\ref{ex:hook:pretxncommit} checks that a commit
296 comment contains a bug ID. If it does, the commit can complete. If
297 not, the commit is rolled back.
299 \section{Writing your own hooks}
301 When you are writing a hook, you might find it useful to run Mercurial
302 either with the \hggopt{-v} option, or the \rcitem{ui}{verbose} config
303 item set to ``true''. When you do so, Mercurial will print a message
304 before it calls each hook.
306 \subsection{Choosing how your hook should run}
307 \label{sec:hook:lang}
309 You can write a hook either as a normal program---typically a shell
310 script---or as a Python function that is executed within the Mercurial
311 process.
313 Writing a hook as an external program has the advantage that it
314 requires no knowledge of Mercurial's internals. You can call normal
315 Mercurial commands to get any added information you need. The
316 trade-off is that external hooks are slower than in-process hooks.
318 An in-process Python hook has complete access to the Mercurial API,
319 and does not ``shell out'' to another process, so it is inherently
320 faster than an external hook. It is also easier to obtain much of the
321 information that a hook requires by using the Mercurial API than by
322 running Mercurial commands.
324 If you are comfortable with Python, or require high performance,
325 writing your hooks in Python may be a good choice. However, when you
326 have a straightforward hook to write and you don't need to care about
327 performance (probably the majority of hooks), a shell script is
328 perfectly fine.
330 \subsection{Hook parameters}
331 \label{sec:hook:param}
333 Mercurial calls each hook with a set of well-defined parameters. In
334 Python, a parameter is passed as a keyword argument to your hook
335 function. For an external program, a parameter is passed as an
336 environment variable.
338 Whether your hook is written in Python or as a shell script, the
339 hook-specific parameter names and values will be the same. A boolean
340 parameter will be represented as a boolean value in Python, but as the
341 number 1 (for ``true'') or 0 (for ``false'') as an environment
342 variable for an external hook. If a hook parameter is named
343 \texttt{foo}, the keyword argument for a Python hook will also be
344 named \texttt{foo}, while the environment variable for an external
345 hook will be named \texttt{HG\_FOO}.
347 \subsection{Hook return values and activity control}
349 A hook that executes successfully must exit with a status of zero if
350 external, or return boolean ``false'' if in-process. Failure is
351 indicated with a non-zero exit status from an external hook, or an
352 in-process hook returning boolean ``true''. If an in-process hook
353 raises an exception, the hook is considered to have failed.
355 For a hook that controls whether an activity can proceed, zero/false
356 means ``allow'', while non-zero/true/exception means ``deny''.
358 \subsection{Writing an external hook}
360 When you define an external hook in your \hgrc\ and the hook is run,
361 its value is passed to your shell, which interprets it. This means
362 that you can use normal shell constructs in the body of the hook.
364 An executable hook is always run with its current directory set to a
365 repository's root directory.
367 Each hook parameter is passed in as an environment variable; the name
368 is upper-cased, and prefixed with the string ``\texttt{HG\_}''.
370 With the exception of hook parameters, Mercurial does not set or
371 modify any environment variables when running a hook. This is useful
372 to remember if you are writing a site-wide hook that may be run by a
373 number of different users with differing environment variables set.
374 In multi-user situations, you should not rely on environment variables
375 being set to the values you have in your environment when testing the
376 hook.
378 \subsection{Telling Mercurial to use an in-process hook}
380 The \hgrc\ syntax for defining an in-process hook is slightly
381 different than for an executable hook. The value of the hook must
382 start with the text ``\texttt{python:}'', and continue with the
383 fully-qualified name of a callable object to use as the hook's value.
385 The module in which a hook lives is automatically imported when a hook
386 is run. So long as you have the module name and \envar{PYTHONPATH}
387 right, it should ``just work''.
389 The following \hgrc\ example snippet illustrates the syntax and
390 meaning of the notions we just described.
391 \begin{codesample2}
392 [hooks]
393 commit.example = python:mymodule.submodule.myhook
394 \end{codesample2}
395 When Mercurial runs the \texttt{commit.example} hook, it imports
396 \texttt{mymodule.submodule}, looks for the callable object named
397 \texttt{myhook}, and calls it.
399 \subsection{Writing an in-process hook}
401 The simplest in-process hook does nothing, but illustrates the basic
402 shape of the hook API:
403 \begin{codesample2}
404 def myhook(ui, repo, **kwargs):
405 pass
406 \end{codesample2}
407 The first argument to a Python hook is always a
408 \pymodclass{mercurial.ui}{ui} object. The second is a repository object;
409 at the moment, it is always an instance of
410 \pymodclass{mercurial.localrepo}{localrepository}. Following these two
411 arguments are other keyword arguments. Which ones are passed in
412 depends on the hook being called, but a hook can ignore arguments it
413 doesn't care about by dropping them into a keyword argument dict, as
414 with \texttt{**kwargs} above.
416 \section{Some hook examples}
418 \subsection{Writing meaningful commit messages}
420 It's hard to imagine a useful commit message being very short. The
421 simple \hook{pretxncommit} hook of figure~\ref{ex:hook:msglen.run}
422 will prevent you from committing a changeset with a message that is
423 less than ten bytes long.
425 \begin{figure}[ht]
426 \interaction{hook.msglen.run}
427 \caption{A hook that forbids overly short commit messages}
428 \label{ex:hook:msglen.run}
429 \end{figure}
431 \subsection{Checking for trailing whitespace}
433 An interesting use of a commit-related hook is to help you to write
434 cleaner code. A simple example of ``cleaner code'' is the dictum that
435 a change should not add any new lines of text that contain ``trailing
436 whitespace''. Trailing whitespace is a series of space and tab
437 characters at the end of a line of text. In most cases, trailing
438 whitespace is unnecessary, invisible noise, but it is occasionally
439 problematic, and people often prefer to get rid of it.
441 You can use either the \hook{precommit} or \hook{pretxncommit} hook to
442 tell whether you have a trailing whitespace problem. If you use the
443 \hook{precommit} hook, the hook will not know which files you are
444 committing, so it will have to check every modified file in the
445 repository for trailing white space. If you want to commit a change
446 to just the file \filename{foo}, but the file \filename{bar} contains
447 trailing whitespace, doing a check in the \hook{precommit} hook will
448 prevent you from committing \filename{foo} due to the problem with
449 \filename{bar}. This doesn't seem right.
451 Should you choose the \hook{pretxncommit} hook, the check won't occur
452 until just before the transaction for the commit completes. This will
453 allow you to check for problems only the exact files that are being
454 committed. However, if you entered the commit message interactively
455 and the hook fails, the transaction will roll back; you'll have to
456 re-enter the commit message after you fix the trailing whitespace and
457 run \hgcmd{commit} again.
459 \begin{figure}[ht]
460 \interaction{hook.ws.simple}
461 \caption{A simple hook that checks for trailing whitespace}
462 \label{ex:hook:ws.simple}
463 \end{figure}
465 Figure~\ref{ex:hook:ws.simple} introduces a simple \hook{pretxncommit}
466 hook that checks for trailing whitespace. This hook is short, but not
467 very helpful. It exits with an error status if a change adds a line
468 with trailing whitespace to any file, but does not print any
469 information that might help us to identify the offending file or
470 line. It also has the nice property of not paying attention to
471 unmodified lines; only lines that introduce new trailing whitespace
472 cause problems.
474 \begin{figure}[ht]
475 \interaction{hook.ws.better}
476 \caption{A better trailing whitespace hook}
477 \label{ex:hook:ws.better}
478 \end{figure}
480 The example of figure~\ref{ex:hook:ws.better} is much more complex,
481 but also more useful. It parses a unified diff to see if any lines
482 add trailing whitespace, and prints the name of the file and the line
483 number of each such occurrence. Even better, if the change adds
484 trailing whitespace, this hook saves the commit comment and prints the
485 name of the save file before exiting and telling Mercurial to roll the
486 transaction back, so you can use
487 \hgcmdargs{commit}{\hgopt{commit}{-l}~\emph{filename}} to reuse the
488 saved commit message once you've corrected the problem.
490 As a final aside, note in figure~\ref{ex:hook:ws.better} the use of
491 \command{perl}'s in-place editing feature to get rid of trailing
492 whitespace from a file. This is concise and useful enough that I will
493 reproduce it here.
494 \begin{codesample2}
495 perl -pi -e 's,\\s+\$,,' filename
496 \end{codesample2}
498 \section{Bundled hooks}
500 Mercurial ships with several bundled hooks. You can find them in the
501 \dirname{hgext} directory of a Mercurial source tree. If you are
502 using a Mercurial binary package, the hooks will be located in the
503 \dirname{hgext} directory of wherever your package installer put
504 Mercurial.
506 \subsection{\hgext{acl}---access control for parts of a repository}
508 The \hgext{acl} extension lets you control which remote users are
509 allowed to push changesets to a networked server. You can protect any
510 portion of a repository (including the entire repo), so that a
511 specific remote user can push changes that do not affect the protected
512 portion.
514 This extension implements access control based on the identity of the
515 user performing a push, \emph{not} on who committed the changesets
516 they're pushing. (If access control based on committer was to work
517 properly, it would require commits to be cryptographically signed,
518 which is an onerous and hence unusual policy to enforce.)
520 XXX More help.
522 \section{Hook reference}
523 \label{sec:hook:ref}
525 \subsection{In-process hook execution}
527 An in-process hook is called with arguments of the following form:
528 \begin{codesample2}
529 def myhook(ui, repo, **kwargs):
530 pass
531 \end{codesample2}
532 The \texttt{ui} parameter is a \pymodclass{mercurial.ui}{ui} object.
533 The \texttt{repo} parameter is a
534 \pymodclass{mercurial.localrepo}{localrepository} object. The
535 names and values of the \texttt{**kwargs} parameters depend on the
536 hook being invoked, with the following common features:
537 \begin{itemize}
538 \item If a parameter is named \texttt{node} or
539 \texttt{parent\emph{N}}, it will contain a hexadecimal changeset ID.
540 The empty string is used to represent ``null changeset ID'' instead
541 of a string of zeroes.
542 \item Boolean-valued parameters are represented as Python
543 \texttt{bool} objects.
544 \end{itemize}
546 An in-process hook is called without a change to the process's working
547 directory (unlike external hooks, which are run in the root of the
548 repository). It must not change the process's working directory. If
549 it were to do so, it would probably cause calls to the Mercurial API,
550 or operations after the hook finishes, to fail.
552 If a hook returns a boolean ``false'' value, it is considered to
553 have succeeded. If it returns a boolean ``true'' value or raises an
554 exception, it is considered to have failed.
556 \subsection{External hook execution}
558 An external hook is passed to the user's shell for execution, so
559 features of that shell, such as variable substitution and command
560 redirection, are available. The hook is run in the root directory of
561 the repository.
563 Hook parameters are passed to the hook as environment variables. Each
564 environment variable's name is converted in upper case and prefixed
565 with the string ``\texttt{HG\_}''. For example, if the name of a
566 parameter is ``\texttt{node}'', the name of the environment variable
567 representing that parameter will be ``\texttt{HG\_NODE}''.
569 A boolean parameter is represented as the string ``\texttt{1}'' for
570 ``true'', ``\texttt{0}'' for ``false''. If an environment variable is
571 named \envar{HG\_NODE}, \envar{HG\_PARENT1} or \envar{HG\_PARENT2}, it
572 contains a changeset ID represented as a hexadecimal string. The
573 empty string is used to represent ``null changeset ID'' instead of a
574 string of zeroes.
576 If a hook exits with a status of zero, it is considered to have
577 succeeded. If it exits with a non-zero status, it is considered to
578 have failed.
580 \subsection{The \hook{changegroup} hook}
581 \label{sec:hook:changegroup}
583 This hook is run after a group of pre-existing changesets has been
584 added to the repository, for example via a \hgcmd{pull} or
585 \hgcmd{unbundle}. This hook is run once per operation that added one
586 or more changesets. This is in contrast to the \hook{incoming} hook,
587 which is run once per changeset, regardless of whether the changesets
588 arrive in a group.
590 Some possible uses for this hook include kicking off an automated
591 build or test of the added changesets, updating a bug database, or
592 notifying subscribers that a repository contains new changes.
594 Parameters to this hook:
595 \begin{itemize}
596 \item[\texttt{node}] A changeset ID. The changeset ID of the first
597 changeset in the group that was added. All changesets between this
598 and \index{tags!\texttt{tip}}\texttt{tip}, inclusive, were added by
599 a single \hgcmd{pull}, \hgcmd{push} or \hgcmd{unbundle}.
600 \end{itemize}
602 See also: \hook{incoming} (section~\ref{sec:hook:incoming}),
603 \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup}),
604 \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
606 \subsection{The \hook{commit} hook}
607 \label{sec:hook:commit}
609 This hook is run after a new changeset has been created.
611 Parameters to this hook:
612 \begin{itemize}
613 \item[\texttt{node}] A changeset ID. The changeset ID of the newly
614 committed changeset.
615 \item[\texttt{parent1}] A changeset ID. The changeset ID of the first
616 parent of the newly committed changeset.
617 \item[\texttt{parent2}] A changeset ID. The changeset ID of the second
618 parent of the newly committed changeset.
619 \end{itemize}
621 See also: \hook{precommit} (section~\ref{sec:hook:precommit}),
622 \hook{pretxncommit} (section~\ref{sec:hook:pretxncommit})
624 \subsection{The \hook{incoming} hook}
625 \label{sec:hook:incoming}
627 This hook is run after a pre-existing changeset has been added to the
628 repository, for example via a \hgcmd{push}. If a group of changesets
629 was added in a single operation, this hook is called once for each
630 added changeset.
632 You can use this hook for the same purposes as the \hook{changegroup}
633 hook (section~\ref{sec:hook:changegroup}); it's simply more convenient
634 sometimes to run a hook once per group of changesets, while other
635 times it's handier once per changeset.
637 Parameters to this hook:
638 \begin{itemize}
639 \item[\texttt{node}] A changeset ID. The ID of the newly added
640 changeset.
641 \end{itemize}
643 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}) \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup}), \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
645 \subsection{The \hook{outgoing} hook}
646 \label{sec:hook:outgoing}
648 This hook is run after a group of changesets has been propagated out
649 of this repository, for example by a \hgcmd{push} or \hgcmd{bundle}
650 command.
652 One possible use for this hook is to notify administrators that
653 changes have been pulled.
655 Parameters to this hook:
656 \begin{itemize}
657 \item[\texttt{node}] A changeset ID. The changeset ID of the first
658 changeset of the group that was sent.
659 \item[\texttt{source}] A string. The source of the of the operation.
660 If a remote client pulled changes from this repository,
661 \texttt{source} will be \texttt{serve}. If the client that obtained
662 changes from this repository was local, \texttt{source} will be
663 \texttt{bundle}, \texttt{pull}, or \texttt{push}, depending on the
664 operation the client performed.
665 \end{itemize}
667 See also: \hook{preoutgoing} (section~\ref{sec:hook:preoutgoing})
669 \subsection{The \hook{prechangegroup} hook}
670 \label{sec:hook:prechangegroup}
672 This controlling hook is run before Mercurial begins to add a group of
673 changesets from another repository.
675 This hook does not have any information about the changesets to be
676 added, because it is run before transmission of those changesets is
677 allowed to begin. If this hook fails, the changesets will not be
678 transmitted.
680 One use for this hook is to prevent external changes from being added
681 to a repository, for example to ``freeze'' a server-hosted branch
682 temporarily or permanently.
684 This hook is not passed any parameters.
686 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}),
687 \hook{incoming} (section~\ref{sec:hook:incoming}), ,
688 \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
690 \subsection{The \hook{precommit} hook}
691 \label{sec:hook:precommit}
693 This hook is run before Mercurial begins to commit a new changeset.
694 It is run before Mercurial has any of the metadata for the commit,
695 such as the files to be committed, the commit message, or the commit
696 date.
698 One use for this hook is to disable the ability to commit new
699 changesets, while still allowing incoming changesets. Another is to
700 run a build or test, and only allow the commit to begin if the build
701 or test succeeds.
703 Parameters to this hook:
704 \begin{itemize}
705 \item[\texttt{parent1}] A changeset ID. The changeset ID of the first
706 parent of the working directory.
707 \item[\texttt{parent2}] A changeset ID. The changeset ID of the second
708 parent of the working directory.
709 \end{itemize}
710 If the commit proceeds, the parents of the working directory will
711 become the parents of the new changeset.
713 See also: \hook{commit} (section~\ref{sec:hook:commit}),
714 \hook{pretxncommit} (section~\ref{sec:hook:pretxncommit})
716 \subsection{The \hook{preoutgoing} hook}
717 \label{sec:hook:preoutgoing}
719 This hook is invoked before Mercurial knows the identities of the
720 changesets to be transmitted.
722 One use for this hook is to prevent changes from being transmitted to
723 another repository.
725 Parameters to this hook:
726 \begin{itemize}
727 \item[\texttt{source}] A string. The source of the operation that is
728 attempting to obtain changes from this repository. See the
729 documentation for the \texttt{source} parameter to the
730 \hook{outgoing} hook, in section~\ref{sec:hook:outgoing}, for
731 possible values of this parameter..
732 \end{itemize}
734 See also: \hook{outgoing} (section~\ref{sec:hook:outgoing})
736 \subsection{The \hook{pretag} hook}
737 \label{sec:hook:pretag}
739 This controlling hook is run before a tag is created. If the hook
740 succeeds, creation of the tag proceeds. If the hook fails, the tag is
741 not created.
743 Parameters to this hook:
744 \begin{itemize}
745 \item[\texttt{local}] A boolean. Whether the tag is local to this
746 repository instance (i.e.~stored in \sfilename{.hg/tags}) or managed
747 by Mercurial (stored in \sfilename{.hgtags}).
748 \item[\texttt{node}] A changeset ID. The ID of the changeset to be tagged.
749 \item[\texttt{tag}] A string. The name of the tag to be created.
750 \end{itemize}
752 If the tag to be created is revision-controlled, the \hook{precommit}
753 and \hook{pretxncommit} hooks (sections~\ref{sec:hook:commit}
754 and~\ref{sec:hook:pretxncommit}) will also be run.
756 See also: \hook{tag} (section~\ref{sec:hook:tag})
758 \subsection{The \hook{pretxnchangegroup} hook}
759 \label{sec:hook:pretxnchangegroup}
761 This controlling hook is run before a transaction---that manages the
762 addition of a group of new changesets from outside the
763 repository---completes. If the hook succeeds, the transaction
764 completes, and all of the changesets become permanent within this
765 repository. If the hook fails, the transaction is rolled back, and
766 the data for the changesets is erased.
768 This hook can access the metadata associated with the almost-added
769 changesets, but it should not do anything permanent with this data.
770 It must also not modify the working directory.
772 While this hook is running, if other Mercurial processes access this
773 repository, they will be able to see the almost-added changesets as if
774 they are permanent. This may lead to race conditions if you do not
775 take steps to avoid them.
777 This hook can be used to automatically vet a group of changesets. If
778 the hook fails, all of the changesets are ``rejected'' when the
779 transaction rolls back.
781 Parameters to this hook are the same as for the \hook{changegroup}
782 hook; see section~\ref{sec:hook:changegroup} for details.
784 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}),
785 \hook{incoming} (section~\ref{sec:hook:incoming}),
786 \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup})
788 \subsection{The \hook{pretxncommit} hook}
789 \label{sec:hook:pretxncommit}
791 This controlling hook is run before a transaction---that manages a new
792 commit---completes. If the hook succeeds, the transaction completes
793 and the changeset becomes permanent within this repository. If the
794 hook fails, the transaction is rolled back, and the commit data is
795 erased.
797 This hook can access the metadata associated with the almost-new
798 changeset, but it should not do anything permanent with this data. It
799 must also not modify the working directory.
801 While this hook is running, if other Mercurial processes access this
802 repository, they will be able to see the almost-new changeset as if it
803 is permanent. This may lead to race conditions if you do not take
804 steps to avoid them.
806 Parameters to this hook are the same as for the \hook{commit} hook;
807 see section~\ref{sec:hook:commit} for details.
809 See also: \hook{precommit} (section~\ref{sec:hook:precommit})
811 \subsection{The \hook{preupdate} hook}
812 \label{sec:hook:preupdate}
814 This controlling hook is run before an update or merge of the working
815 directory begins. It is run only if Mercurial's normal pre-update
816 checks determine that the update or merge can proceed. If the hook
817 succeeds, the update or merge may proceed; if it fails, the update or
818 merge does not start.
820 Parameters to this hook:
821 \begin{itemize}
822 \item[\texttt{parent1}] A changeset ID. The ID of the parent that the
823 working directory is to be updated to. If the working directory is
824 being merged, it will not change this parent.
825 \item[\texttt{parent2}] A changeset ID. Only set if the working
826 directory is being merged. The ID of the revision that the working
827 directory is being merged with.
828 \end{itemize}
830 See also: \hook{update} (section~\ref{sec:hook:update})
832 \subsection{The \hook{tag} hook}
833 \label{sec:hook:tag}
835 This hook is run after a tag has been created.
837 Parameters to this hook are the same as for the \hook{pretag} hook;
838 see section~\ref{sec:hook:pretag} for details.
840 If the created tag is revision-controlled, the \hook{commit} hook
841 (section~\ref{sec:hook:commit}) is run before this hook.
843 See also: \hook{pretag} (section~\ref{sec:hook:pretag})
845 \subsection{The \hook{update} hook}
846 \label{sec:hook:update}
848 This hook is run after an update or merge of the working directory
849 completes. Since a merge can fail (if the external \command{hgmerge}
850 command fails to resolve conflicts in a file), this hook communicates
851 whether the update or merge completed cleanly.
853 \begin{itemize}
854 \item[\texttt{error}] A boolean. Indicates whether the update or
855 merge completed successfully.
856 \item[\texttt{parent1}] A changeset ID. The ID of the parent that the
857 working directory was updated to. If the working directory was
858 merged, it will not have changed this parent.
859 \item[\texttt{parent2}] A changeset ID. Only set if the working
860 directory was merged. The ID of the revision that the working
861 directory was merged with.
862 \end{itemize}
864 See also: \hook{preupdate} (section~\ref{sec:hook:preupdate})
866 %%% Local Variables:
867 %%% mode: latex
868 %%% TeX-master: "00book"
869 %%% End: