hgbook
view en/hook.tex @ 41:d1a3394f8bcf
More hook content.
| author | Bryan O'Sullivan <bos@serpentine.com> |
|---|---|
| date | Thu Jul 20 19:42:50 2006 -0700 (2006-07-20) |
| parents | b2fe9964b21b |
| children | 012df94a02fe b727a63518d4 |
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 ahred 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 te 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} Python, while the environment variable for an
345 external 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{Hook reference}
417 \label{sec:hook:ref}
419 \subsection{In-process hook execution}
421 An in-process hook is called with arguments of the following form:
422 \begin{codesample2}
423 def myhook(ui, repo, **kwargs):
424 pass
425 \end{codesample2}
426 The \texttt{ui} parameter is a \pymodclass{mercurial.ui}{ui} object.
427 The \texttt{repo} parameter is a
428 \pymodclass{mercurial.localrepo}{localrepository} object. The
429 names and values of the \texttt{**kwargs} parameters depend on the
430 hook being invoked, with the following common features:
431 \begin{itemize}
432 \item If a parameter is named \texttt{node} or
433 \texttt{parent\emph{N}}, it will contain a hexadecimal changeset ID.
434 The empty string is used to represent ``null changeset ID'' instead
435 of a string of zeroes.
436 \item Boolean-valued parameters are represented as Python
437 \texttt{bool} objects.
438 \end{itemize}
440 An in-process hook is called without a change to the process's working
441 directory (unlike external hooks, which are run in the root of the
442 repository). It must not change the process's working directory. If
443 it were to do so, it would probably cause calls to the Mercurial API,
444 or operations after the hook finishes, to fail.
446 If a hook returns a boolean ``false'' value, it is considered to
447 have succeeded. If it returns a boolean ``true'' value or raises an
448 exception, it is considered to have failed.
450 \subsection{External hook execution}
452 An external hook is passed to the user's shell for execution, so
453 features of that shell, such as variable substitution and command
454 redirection, are available. The hook is run in the root directory of
455 the repository.
457 Hook parameters are passed to the hook as environment variables. Each
458 environment variable's name is converted in upper case and prefixed
459 with the string ``\texttt{HG\_}''. For example, if the name of a
460 parameter is ``\texttt{node}'', the name of the environment variable
461 representing that parameter will be ``\texttt{HG\_NODE}''.
463 A boolean parameter is represented as the string ``\texttt{1}'' for
464 ``true'', ``\texttt{0}'' for ``false''. If an environment variable is
465 named \envar{HG\_NODE}, \envar{HG\_PARENT1} or \envar{HG\_PARENT2}, it
466 contains a changeset ID represented as a hexadecimal string. The
467 empty string is used to represent ``null changeset ID'' instead of a
468 string of zeroes.
470 If a hook exits with a status of zero, it is considered to have
471 succeeded. If it exits with a non-zero status, it is considered to
472 have failed.
474 \subsection{The \hook{changegroup} hook}
475 \label{sec:hook:changegroup}
477 This hook is run after a group of pre-existing changesets has been
478 added to the repository, for example via a \hgcmd{pull} or
479 \hgcmd{unbundle}. This hook is run once per operation that added one
480 or more changesets. This is in contrast to the \hook{incoming} hook,
481 which is run once per changeset, regardless of whether the changesets
482 arrive in a group.
484 Some possible uses for this hook include kicking off an automated
485 build or test of the added changesets, updating a bug database, or
486 notifying subscribers that a repository contains new changes.
488 Parameters to this hook:
489 \begin{itemize}
490 \item[\texttt{node}] A changeset ID. The changeset ID of the first
491 changeset in the group that was added. All changesets between this
492 and \index{tags!\texttt{tip}}\texttt{tip}, inclusive, were added by
493 a single \hgcmd{pull}, \hgcmd{push} or \hgcmd{unbundle}.
494 \end{itemize}
496 See also: \hook{incoming} (section~\ref{sec:hook:incoming}),
497 \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup}),
498 \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
500 \subsection{The \hook{commit} hook}
501 \label{sec:hook:commit}
503 This hook is run after a new changeset has been created.
505 Parameters to this hook:
506 \begin{itemize}
507 \item[\texttt{node}] A changeset ID. The changeset ID of the newly
508 committed changeset.
509 \item[\texttt{parent1}] A changeset ID. The changeset ID of the first
510 parent of the newly committed changeset.
511 \item[\texttt{parent2}] A changeset ID. The changeset ID of the second
512 parent of the newly committed changeset.
513 \end{itemize}
515 See also: \hook{precommit} (section~\ref{sec:hook:precommit}),
516 \hook{pretxncommit} (section~\ref{sec:hook:pretxncommit})
518 \subsection{The \hook{incoming} hook}
519 \label{sec:hook:incoming}
521 This hook is run after a pre-existing changeset has been added to the
522 repository, for example via a \hgcmd{push}. If a group of changesets
523 was added in a single operation, this hook is called once for each
524 added changeset.
526 You can use this hook for the same purposes as the \hook{changegroup}
527 hook (section~\ref{sec:hook:changegroup}); it's simply more convenient
528 sometimes to run a hook once per group of changesets, while othher
529 times it's handier once per changeset.
531 Parameters to this hook:
532 \begin{itemize}
533 \item[\texttt{node}] A changeset ID. The ID of the newly added
534 changeset.
535 \end{itemize}
537 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}) \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup}), \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
539 \subsection{The \hook{outgoing} hook}
540 \label{sec:hook:outgoing}
542 This hook is run after a group of changesets has been propagated out
543 of this repository, for example by a \hgcmd{push} or \hgcmd{bundle}
544 command.
546 One possible use for this hook is to notify administrators that
547 changes have been pulled.
549 Parameters to this hook:
550 \begin{itemize}
551 \item[\texttt{node}] A changeset ID. The changeset ID of the first
552 changeset of the group that was sent.
553 \item[\texttt{source}] A string. The source of the of the operation.
554 If a remote client pulled changes from this repository,
555 \texttt{source} will be \texttt{serve}. If the client that obtained
556 changes from this repository was local, \texttt{source} will be
557 \texttt{bundle}, \texttt{pull}, or \texttt{push}, depending on the
558 operation the client performed.
559 \end{itemize}
561 See also: \hook{preoutgoing} (section~\ref{sec:hook:preoutgoing})
563 \subsection{The \hook{prechangegroup} hook}
564 \label{sec:hook:prechangegroup}
566 This controlling hook is run before Mercurial begins to add a group of
567 changesets from another repository.
569 This hook does not have any information about the changesets to be
570 added, because it is run before transmission of those changesets is
571 allowed to begin. If this hook fails, the changesets will not be
572 transmitted.
574 One use for this hook is to prevent external changes from being added
575 to a repository, for example to ``freeze'' a server-hosted branch
576 temporarily or permanently.
578 This hook is not passed any parameters.
580 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}),
581 \hook{incoming} (section~\ref{sec:hook:incoming}), ,
582 \hook{pretxnchangegroup} (section~\ref{sec:hook:pretxnchangegroup})
584 \subsection{The \hook{precommit} hook}
585 \label{sec:hook:precommit}
587 This hook is run before Mercurial begins to commit a new changeset.
588 It is run before Mercurial has any of the metadata for the commit,
589 such as the files to be committed, the commit message, or the commit
590 date.
592 One use for this hook is to disable the ability to commit new
593 changesets, while still allowing incoming changesets. Another is to
594 run a build or test, and only allow the commit to begin if the build
595 or test succeeds.
597 Parameters to this hook:
598 \begin{itemize}
599 \item[\texttt{parent1}] A changeset ID. The changeset ID of the first
600 parent of the working directory.
601 \item[\texttt{parent2}] A changeset ID. The changeset ID of the second
602 parent of the working directory.
603 \end{itemize}
604 If the commit proceeds, the parents of the working directory will
605 become the parents of the new changeset.
607 See also: \hook{commit} (section~\ref{sec:hook:commit}),
608 \hook{pretxncommit} (section~\ref{sec:hook:pretxncommit})
610 \subsection{The \hook{preoutgoing} hook}
611 \label{sec:hook:preoutgoing}
613 This hook is invoked before Mercurial knows the identities of the
614 changesets to be transmitted.
616 One use for this hook is to prevent changes from being transmitted to
617 another repository.
619 Parameters to this hook:
620 \begin{itemize}
621 \item[\texttt{source}] A string. The source of the operation that is
622 attempting to obtain changes from this repository. See the
623 documentation for the \texttt{source} parameter to the
624 \hook{outgoing} hook, in section~\ref{sec:hook:outgoing}, for
625 possible values of this parameter..
626 \end{itemize}
628 See also: \hook{outgoing} (section~\ref{sec:hook:outgoing})
630 \subsection{The \hook{pretag} hook}
631 \label{sec:hook:pretag}
633 This controlling hook is run before a tag is created. If the hook
634 succeeds, creation of the tag proceeds. If the hook fails, the tag is
635 not created.
637 Parameters to this hook:
638 \begin{itemize}
639 \item[\texttt{local}] A boolean. Whether the tag is local to this
640 repository instance (i.e.~stored in \sfilename{.hg/tags}) or managed
641 by Mercurial (stored in \sfilename{.hgtags}).
642 \item[\texttt{node}] A changeset ID. The ID of the changeset to be tagged.
643 \item[\texttt{tag}] A string. The name of the tag to be created.
644 \end{itemize}
646 If the tag to be created is revision-controlled, the \hook{precommit}
647 and \hook{pretxncommit} hooks (sections~\ref{sec:hook:commit}
648 and~\ref{sec:hook:pretxncommit}) will also be run.
650 See also: \hook{tag} (section~\ref{sec:hook:tag})
652 \subsection{The \hook{pretxnchangegroup} hook}
653 \label{sec:hook:pretxnchangegroup}
655 This controlling hook is run before a transaction---that manages the
656 addition of a group of new changesets from outside the
657 repository---completes. If the hook succeeds, the transaction
658 completes, and all of the changesets become permanent within this
659 repository. If the hook fails, the transaction is rolled back, and
660 the data for the changesets is erased.
662 This hook can access the metadata associated with the almost-added
663 changesets, but it should not do anything permanent with this data.
664 It must also not modify the working directory.
666 While this hook is running, if other Mercurial processes access this
667 repository, they will be able to see the almost-added changesets as if
668 they are permanent. This may lead to race conditions if you do not
669 take steps to avoid them.
671 This hook can be used to automatically vet a group of changesets. If
672 the hook fails, all of the changesets are ``rejected'' when the
673 transaction rolls back.
675 Parameters to this hook are the same as for the \hook{changegroup}
676 hook; see section~\ref{sec:hook:changegroup} for details.
678 See also: \hook{changegroup} (section~\ref{sec:hook:changegroup}),
679 \hook{incoming} (section~\ref{sec:hook:incoming}),
680 \hook{prechangegroup} (section~\ref{sec:hook:prechangegroup})
682 \subsection{The \hook{pretxncommit} hook}
683 \label{sec:hook:pretxncommit}
685 This controlling hook is run before a transaction---that manages a new
686 commit---completes. If the hook succeeds, the transaction completes
687 and the changeset becomes permanent within this repository. If the
688 hook fails, the transaction is rolled back, and the commit data is
689 erased.
691 This hook can access the metadata associated with the almost-new
692 changeset, but it should not do anything permanent with this data. It
693 must also not modify the working directory.
695 While this hook is running, if other Mercurial processes access this
696 repository, they will be able to see the almost-new changeset as if it
697 is permanent. This may lead to race conditions if you do not take
698 steps to avoid them.
700 Parameters to this hook are the same as for the \hook{commit} hook;
701 see section~\ref{sec:hook:commit} for details.
703 See also: \hook{precommit} (section~\ref{sec:hook:precommit})
705 \subsection{The \hook{preupdate} hook}
706 \label{sec:hook:preupdate}
708 This controlling hook is run before an update or merge of the working
709 directory begins. It is run only if Mercurial's normal pre-update
710 checks determine that the update or merge can proceed. If the hook
711 succeeds, the update or merge may proceed; if it fails, the update or
712 merge does not start.
714 Parameters to this hook:
715 \begin{itemize}
716 \item[\texttt{parent1}] A changeset ID. The ID of the parent that the
717 working directory is to be updated to. If the working directory is
718 being merged, it will not change this parent.
719 \item[\texttt{parent2}] A changeset ID. Only set if the working
720 directory is being merged. The ID of the revision that the working
721 directory is being merged with.
722 \end{itemize}
724 See also: \hook{update} (section~\ref{sec:hook:update})
726 \subsection{The \hook{tag} hook}
727 \label{sec:hook:tag}
729 This hook is run after a tag has been created.
731 Parameters to this hook are the same as for the \hook{pretag} hook;
732 see section~\ref{sec:hook:pretag} for details.
734 If the created tag is revision-controlled, the \hook{commit} hook
735 (section~\ref{sec:hook:commit}) is run before this hook.
737 See also: \hook{pretag} (section~\ref{sec:hook:pretag})
739 \subsection{The \hook{update} hook}
740 \label{sec:hook:update}
742 This hook is run after an update or merge of the working directory
743 completes. Since a merge can fail (if the external \command{hgmerge}
744 command fails to resolve conflicts in a file), this hook communicates
745 whether the update or merge completed cleanly.
747 \begin{itemize}
748 \item[\texttt{error}] A boolean. Indicates whether the update or
749 merge completed successfully.
750 \item[\texttt{parent1}] A changeset ID. The ID of the parent that the
751 working directory was updated to. If the working directory was
752 merged, it will not have changed this parent.
753 \item[\texttt{parent2}] A changeset ID. Only set if the working
754 directory was merged. The ID of the revision that the working
755 directory was merged with.
756 \end{itemize}
758 See also: \hook{preupdate} (section~\ref{sec:hook:preupdate})
760 %%% Local Variables:
761 %%% mode: latex
762 %%% TeX-master: "00book"
763 %%% End: