Merge branch 'lt/case-insensitive'
[git/git.git] / Documentation / hooks.txt
1 Hooks used by git
2 =================
3
4 Hooks are little scripts you can place in `$GIT_DIR/hooks`
5 directory to trigger action at certain points. When
6 `git-init` is run, a handful example hooks are copied in the
7 `hooks` directory of the new repository, but by default they are
8 all disabled. To enable a hook, make it executable with `chmod +x`.
9
10 This document describes the currently defined hooks.
11
12 applypatch-msg
13 --------------
14
15 This hook is invoked by `git-am` script. It takes a single
16 parameter, the name of the file that holds the proposed commit
17 log message. Exiting with non-zero status causes
18 `git-am` to abort before applying the patch.
19
20 The hook is allowed to edit the message file in place, and can
21 be used to normalize the message into some project standard
22 format (if the project has one). It can also be used to refuse
23 the commit after inspecting the message file.
24
25 The default 'applypatch-msg' hook, when enabled, runs the
26 'commit-msg' hook, if the latter is enabled.
27
28 pre-applypatch
29 --------------
30
31 This hook is invoked by `git-am`. It takes no parameter, and is
32 invoked after the patch is applied, but before a commit is made.
33
34 If it exits with non-zero status, then the working tree will not be
35 committed after applying the patch.
36
37 It can be used to inspect the current working tree and refuse to
38 make a commit if it does not pass certain test.
39
40 The default 'pre-applypatch' hook, when enabled, runs the
41 'pre-commit' hook, if the latter is enabled.
42
43 post-applypatch
44 ---------------
45
46 This hook is invoked by `git-am`. It takes no parameter,
47 and is invoked after the patch is applied and a commit is made.
48
49 This hook is meant primarily for notification, and cannot affect
50 the outcome of `git-am`.
51
52 pre-commit
53 ----------
54
55 This hook is invoked by `git-commit`, and can be bypassed
56 with `\--no-verify` option. It takes no parameter, and is
57 invoked before obtaining the proposed commit log message and
58 making a commit. Exiting with non-zero status from this script
59 causes the `git-commit` to abort.
60
61 The default 'pre-commit' hook, when enabled, catches introduction
62 of lines with trailing whitespaces and aborts the commit when
63 such a line is found.
64
65 All the `git-commit` hooks are invoked with the environment
66 variable `GIT_EDITOR=:` if the command will not bring up an editor
67 to modify the commit message.
68
69 prepare-commit-msg
70 ------------------
71
72 This hook is invoked by `git-commit` right after preparing the
73 default log message, and before the editor is started.
74
75 It takes one to three parameters. The first is the name of the file
76 that the commit log message. The second is the source of the commit
77 message, and can be: `message` (if a `\-m` or `\-F` option was
78 given); `template` (if a `\-t` option was given or the
79 configuration option `commit.template` is set); `merge` (if the
80 commit is a merge or a `.git/MERGE_MSG` file exists); `squash`
81 (if a `.git/SQUASH_MSG` file exists); or `commit`, followed by
82 a commit SHA1 (if a `\-c`, `\-C` or `\--amend` option was given).
83
84 If the exit status is non-zero, `git-commit` will abort.
85
86 The purpose of the hook is to edit the message file in place, and
87 it is not suppressed by the `\--no-verify` option. A non-zero exit
88 means a failure of the hook and aborts the commit. It should not
89 be used as replacement for pre-commit hook.
90
91 The sample `prepare-commit-msg` hook that comes with git comments
92 out the `Conflicts:` part of a merge's commit message.
93
94 commit-msg
95 ----------
96
97 This hook is invoked by `git-commit`, and can be bypassed
98 with `\--no-verify` option. It takes a single parameter, the
99 name of the file that holds the proposed commit log message.
100 Exiting with non-zero status causes the `git-commit` to
101 abort.
102
103 The hook is allowed to edit the message file in place, and can
104 be used to normalize the message into some project standard
105 format (if the project has one). It can also be used to refuse
106 the commit after inspecting the message file.
107
108 The default 'commit-msg' hook, when enabled, detects duplicate
109 "Signed-off-by" lines, and aborts the commit if one is found.
110
111 post-commit
112 -----------
113
114 This hook is invoked by `git-commit`. It takes no
115 parameter, and is invoked after a commit is made.
116
117 This hook is meant primarily for notification, and cannot affect
118 the outcome of `git-commit`.
119
120 post-checkout
121 -----------
122
123 This hook is invoked when a `git-checkout` is run after having updated the
124 worktree. The hook is given three parameters: the ref of the previous HEAD,
125 the ref of the new HEAD (which may or may not have changed), and a flag
126 indicating whether the checkout was a branch checkout (changing branches,
127 flag=1) or a file checkout (retrieving a file from the index, flag=0).
128 This hook cannot affect the outcome of `git-checkout`.
129
130 This hook can be used to perform repository validity checks, auto-display
131 differences from the previous HEAD if different, or set working dir metadata
132 properties.
133
134 post-merge
135 -----------
136
137 This hook is invoked by `git-merge`, which happens when a `git pull`
138 is done on a local repository. The hook takes a single parameter, a status
139 flag specifying whether or not the merge being done was a squash merge.
140 This hook cannot affect the outcome of `git-merge` and is not executed,
141 if the merge failed due to conflicts.
142
143 This hook can be used in conjunction with a corresponding pre-commit hook to
144 save and restore any form of metadata associated with the working tree
145 (eg: permissions/ownership, ACLS, etc). See contrib/hooks/setgitperms.perl
146 for an example of how to do this.
147
148 [[pre-receive]]
149 pre-receive
150 -----------
151
152 This hook is invoked by `git-receive-pack` on the remote repository,
153 which happens when a `git push` is done on a local repository.
154 Just before starting to update refs on the remote repository, the
155 pre-receive hook is invoked. Its exit status determines the success
156 or failure of the update.
157
158 This hook executes once for the receive operation. It takes no
159 arguments, but for each ref to be updated it receives on standard
160 input a line of the format:
161
162 <old-value> SP <new-value> SP <ref-name> LF
163
164 where `<old-value>` is the old object name stored in the ref,
165 `<new-value>` is the new object name to be stored in the ref and
166 `<ref-name>` is the full name of the ref.
167 When creating a new ref, `<old-value>` is 40 `0`.
168
169 If the hook exits with non-zero status, none of the refs will be
170 updated. If the hook exits with zero, updating of individual refs can
171 still be prevented by the <<update,'update'>> hook.
172
173 Both standard output and standard error output are forwarded to
174 `git-send-pack` on the other end, so you can simply `echo` messages
175 for the user.
176
177 [[update]]
178 update
179 ------
180
181 This hook is invoked by `git-receive-pack` on the remote repository,
182 which happens when a `git push` is done on a local repository.
183 Just before updating the ref on the remote repository, the update hook
184 is invoked. Its exit status determines the success or failure of
185 the ref update.
186
187 The hook executes once for each ref to be updated, and takes
188 three parameters:
189
190 - the name of the ref being updated,
191 - the old object name stored in the ref,
192 - and the new objectname to be stored in the ref.
193
194 A zero exit from the update hook allows the ref to be updated.
195 Exiting with a non-zero status prevents `git-receive-pack`
196 from updating that ref.
197
198 This hook can be used to prevent 'forced' update on certain refs by
199 making sure that the object name is a commit object that is a
200 descendant of the commit object named by the old object name.
201 That is, to enforce a "fast forward only" policy.
202
203 It could also be used to log the old..new status. However, it
204 does not know the entire set of branches, so it would end up
205 firing one e-mail per ref when used naively, though. The
206 <<post-receive,'post-receive'>> hook is more suited to that.
207
208 Another use suggested on the mailing list is to use this hook to
209 implement access control which is finer grained than the one
210 based on filesystem group.
211
212 Both standard output and standard error output are forwarded to
213 `git-send-pack` on the other end, so you can simply `echo` messages
214 for the user.
215
216 The default 'update' hook, when enabled--and with
217 `hooks.allowunannotated` config option turned on--prevents
218 unannotated tags to be pushed.
219
220 [[post-receive]]
221 post-receive
222 ------------
223
224 This hook is invoked by `git-receive-pack` on the remote repository,
225 which happens when a `git push` is done on a local repository.
226 It executes on the remote repository once after all the refs have
227 been updated.
228
229 This hook executes once for the receive operation. It takes no
230 arguments, but gets the same information as the
231 <<pre-receive,'pre-receive'>>
232 hook does on its standard input.
233
234 This hook does not affect the outcome of `git-receive-pack`, as it
235 is called after the real work is done.
236
237 This supersedes the <<post-update,'post-update'>> hook in that it gets
238 both old and new values of all the refs in addition to their
239 names.
240
241 Both standard output and standard error output are forwarded to
242 `git-send-pack` on the other end, so you can simply `echo` messages
243 for the user.
244
245 The default 'post-receive' hook is empty, but there is
246 a sample script `post-receive-email` provided in the `contrib/hooks`
247 directory in git distribution, which implements sending commit
248 emails.
249
250 [[post-update]]
251 post-update
252 -----------
253
254 This hook is invoked by `git-receive-pack` on the remote repository,
255 which happens when a `git push` is done on a local repository.
256 It executes on the remote repository once after all the refs have
257 been updated.
258
259 It takes a variable number of parameters, each of which is the
260 name of ref that was actually updated.
261
262 This hook is meant primarily for notification, and cannot affect
263 the outcome of `git-receive-pack`.
264
265 The 'post-update' hook can tell what are the heads that were pushed,
266 but it does not know what their original and updated values are,
267 so it is a poor place to do log old..new. The
268 <<post-receive,'post-receive'>> hook does get both original and
269 updated values of the refs. You might consider it instead if you need
270 them.
271
272 When enabled, the default 'post-update' hook runs
273 `git-update-server-info` to keep the information used by dumb
274 transports (e.g., HTTP) up-to-date. If you are publishing
275 a git repository that is accessible via HTTP, you should
276 probably enable this hook.
277
278 Both standard output and standard error output are forwarded to
279 `git-send-pack` on the other end, so you can simply `echo` messages
280 for the user.
281
282 pre-auto-gc
283 -----------
284
285 This hook is invoked by `git-gc --auto`. It takes no parameter, and
286 exiting with non-zero status from this script causes the `git-gc --auto`
287 to abort.