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[thirdparty/git.git] / Documentation / SubmittingPatches
1 Submitting Patches
2 ==================
3
4 == Guidelines
5
6 Here are some guidelines for people who want to contribute their code to this
7 software. There is also a link:MyFirstContribution.html[step-by-step tutorial]
8 available which covers many of these same guidelines.
9
10 [[base-branch]]
11 === Decide what to base your work on.
12
13 In general, always base your work on the oldest branch that your
14 change is relevant to.
15
16 * A bugfix should be based on `maint` in general. If the bug is not
17 present in `maint`, base it on `master`. For a bug that's not yet
18 in `master`, find the topic that introduces the regression, and
19 base your work on the tip of the topic.
20
21 * A new feature should be based on `master` in general. If the new
22 feature depends on a topic that is in `seen`, but not in `master`,
23 base your work on the tip of that topic.
24
25 * Corrections and enhancements to a topic not yet in `master` should
26 be based on the tip of that topic. If the topic has not been merged
27 to `next`, it's alright to add a note to squash minor corrections
28 into the series.
29
30 * In the exceptional case that a new feature depends on several topics
31 not in `master`, start working on `next` or `seen` privately and send
32 out patches for discussion. Before the final merge, you may have to
33 wait until some of the dependent topics graduate to `master`, and
34 rebase your work.
35
36 * Some parts of the system have dedicated maintainers with their own
37 repositories (see the section "Subsystems" below). Changes to
38 these parts should be based on their trees.
39
40 To find the tip of a topic branch, run `git log --first-parent
41 master..seen` and look for the merge commit. The second parent of this
42 commit is the tip of the topic branch.
43
44 [[separate-commits]]
45 === Make separate commits for logically separate changes.
46
47 Unless your patch is really trivial, you should not be sending
48 out a patch that was generated between your working tree and
49 your commit head. Instead, always make a commit with complete
50 commit message and generate a series of patches from your
51 repository. It is a good discipline.
52
53 Give an explanation for the change(s) that is detailed enough so
54 that people can judge if it is good thing to do, without reading
55 the actual patch text to determine how well the code does what
56 the explanation promises to do.
57
58 If your description starts to get too long, that's a sign that you
59 probably need to split up your commit to finer grained pieces.
60 That being said, patches which plainly describe the things that
61 help reviewers check the patch, and future maintainers understand
62 the code, are the most beautiful patches. Descriptions that summarize
63 the point in the subject well, and describe the motivation for the
64 change, the approach taken by the change, and if relevant how this
65 differs substantially from the prior version, are all good things
66 to have.
67
68 Make sure that you have tests for the bug you are fixing. See
69 `t/README` for guidance.
70
71 [[tests]]
72 When adding a new feature, make sure that you have new tests to show
73 the feature triggers the new behavior when it should, and to show the
74 feature does not trigger when it shouldn't. After any code change, make
75 sure that the entire test suite passes.
76
77 If you have an account at GitHub (and you can get one for free to work
78 on open source projects), you can use their Travis CI integration to
79 test your changes on Linux, Mac (and hopefully soon Windows). See
80 GitHub-Travis CI hints section for details.
81
82 Do not forget to update the documentation to describe the updated
83 behavior and make sure that the resulting documentation set formats
84 well (try the Documentation/doc-diff script).
85
86 We currently have a liberal mixture of US and UK English norms for
87 spelling and grammar, which is somewhat unfortunate. A huge patch that
88 touches the files all over the place only to correct the inconsistency
89 is not welcome, though. Potential clashes with other changes that can
90 result from such a patch are not worth it. We prefer to gradually
91 reconcile the inconsistencies in favor of US English, with small and
92 easily digestible patches, as a side effect of doing some other real
93 work in the vicinity (e.g. rewriting a paragraph for clarity, while
94 turning en_UK spelling to en_US). Obvious typographical fixes are much
95 more welcomed ("teh -> "the"), preferably submitted as independent
96 patches separate from other documentation changes.
97
98 [[whitespace-check]]
99 Oh, another thing. We are picky about whitespaces. Make sure your
100 changes do not trigger errors with the sample pre-commit hook shipped
101 in `templates/hooks--pre-commit`. To help ensure this does not happen,
102 run `git diff --check` on your changes before you commit.
103
104 [[describe-changes]]
105 === Describe your changes well.
106
107 The first line of the commit message should be a short description (50
108 characters is the soft limit, see DISCUSSION in linkgit:git-commit[1]),
109 and should skip the full stop. It is also conventional in most cases to
110 prefix the first line with "area: " where the area is a filename or
111 identifier for the general area of the code being modified, e.g.
112
113 * doc: clarify distinction between sign-off and pgp-signing
114 * githooks.txt: improve the intro section
115
116 If in doubt which identifier to use, run `git log --no-merges` on the
117 files you are modifying to see the current conventions.
118
119 [[summary-section]]
120 It's customary to start the remainder of the first line after "area: "
121 with a lower-case letter. E.g. "doc: clarify...", not "doc:
122 Clarify...", or "githooks.txt: improve...", not "githooks.txt:
123 Improve...".
124
125 [[meaningful-message]]
126 The body should provide a meaningful commit message, which:
127
128 . explains the problem the change tries to solve, i.e. what is wrong
129 with the current code without the change.
130
131 . justifies the way the change solves the problem, i.e. why the
132 result with the change is better.
133
134 . alternate solutions considered but discarded, if any.
135
136 [[imperative-mood]]
137 Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
138 instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
139 to do frotz", as if you are giving orders to the codebase to change
140 its behavior. Try to make sure your explanation can be understood
141 without external resources. Instead of giving a URL to a mailing list
142 archive, summarize the relevant points of the discussion.
143
144 [[commit-reference]]
145 If you want to reference a previous commit in the history of a stable
146 branch, use the format "abbreviated hash (subject, date)", like this:
147
148 ....
149 Commit f86a374 (pack-bitmap.c: fix a memleak, 2015-03-30)
150 noticed that ...
151 ....
152
153 The "Copy commit summary" command of gitk can be used to obtain this
154 format (with the subject enclosed in a pair of double-quotes), or this
155 invocation of `git show`:
156
157 ....
158 git show -s --pretty=reference <commit>
159 ....
160
161 or, on an older version of Git without support for --pretty=reference:
162
163 ....
164 git show -s --date=short --pretty='format:%h (%s, %ad)' <commit>
165 ....
166
167 [[git-tools]]
168 === Generate your patch using Git tools out of your commits.
169
170 Git based diff tools generate unidiff which is the preferred format.
171
172 You do not have to be afraid to use `-M` option to `git diff` or
173 `git format-patch`, if your patch involves file renames. The
174 receiving end can handle them just fine.
175
176 [[review-patch]]
177 Please make sure your patch does not add commented out debugging code,
178 or include any extra files which do not relate to what your patch
179 is trying to achieve. Make sure to review
180 your patch after generating it, to ensure accuracy. Before
181 sending out, please make sure it cleanly applies to the `master`
182 branch head. If you are preparing a work based on "next" branch,
183 that is fine, but please mark it as such.
184
185 [[send-patches]]
186 === Sending your patches.
187
188 :security-ml: footnoteref:[security-ml,The Git Security mailing list: git-security@googlegroups.com]
189
190 Before sending any patches, please note that patches that may be
191 security relevant should be submitted privately to the Git Security
192 mailing list{security-ml}, instead of the public mailing list.
193
194 Learn to use format-patch and send-email if possible. These commands
195 are optimized for the workflow of sending patches, avoiding many ways
196 your existing e-mail client that is optimized for "multipart/*" mime
197 type e-mails to corrupt and render your patches unusable.
198
199 People on the Git mailing list need to be able to read and
200 comment on the changes you are submitting. It is important for
201 a developer to be able to "quote" your changes, using standard
202 e-mail tools, so that they may comment on specific portions of
203 your code. For this reason, each patch should be submitted
204 "inline" in a separate message.
205
206 Multiple related patches should be grouped into their own e-mail
207 thread to help readers find all parts of the series. To that end,
208 send them as replies to either an additional "cover letter" message
209 (see below), the first patch, or the respective preceding patch.
210
211 If your log message (including your name on the
212 `Signed-off-by` trailer) is not writable in ASCII, make sure that
213 you send off a message in the correct encoding.
214
215 WARNING: Be wary of your MUAs word-wrap
216 corrupting your patch. Do not cut-n-paste your patch; you can
217 lose tabs that way if you are not careful.
218
219 It is a common convention to prefix your subject line with
220 [PATCH]. This lets people easily distinguish patches from other
221 e-mail discussions. Use of markers in addition to PATCH within
222 the brackets to describe the nature of the patch is also
223 encouraged. E.g. [RFC PATCH] (where RFC stands for "request for
224 comments") is often used to indicate a patch needs further
225 discussion before being accepted, [PATCH v2], [PATCH v3] etc.
226 are often seen when you are sending an update to what you have
227 previously sent.
228
229 The `git format-patch` command follows the best current practice to
230 format the body of an e-mail message. At the beginning of the
231 patch should come your commit message, ending with the
232 `Signed-off-by` trailers, and a line that consists of three dashes,
233 followed by the diffstat information and the patch itself. If
234 you are forwarding a patch from somebody else, optionally, at
235 the beginning of the e-mail message just before the commit
236 message starts, you can put a "From: " line to name that person.
237 To change the default "[PATCH]" in the subject to "[<text>]", use
238 `git format-patch --subject-prefix=<text>`. As a shortcut, you
239 can use `--rfc` instead of `--subject-prefix="RFC PATCH"`, or
240 `-v <n>` instead of `--subject-prefix="PATCH v<n>"`.
241
242 You often want to add additional explanation about the patch,
243 other than the commit message itself. Place such "cover letter"
244 material between the three-dash line and the diffstat. For
245 patches requiring multiple iterations of review and discussion,
246 an explanation of changes between each iteration can be kept in
247 Git-notes and inserted automatically following the three-dash
248 line via `git format-patch --notes`.
249
250 [[attachment]]
251 Do not attach the patch as a MIME attachment, compressed or not.
252 Do not let your e-mail client send quoted-printable. Do not let
253 your e-mail client send format=flowed which would destroy
254 whitespaces in your patches. Many
255 popular e-mail applications will not always transmit a MIME
256 attachment as plain text, making it impossible to comment on
257 your code. A MIME attachment also takes a bit more time to
258 process. This does not decrease the likelihood of your
259 MIME-attached change being accepted, but it makes it more likely
260 that it will be postponed.
261
262 Exception: If your mailer is mangling patches then someone may ask
263 you to re-send them using MIME, that is OK.
264
265 [[pgp-signature]]
266 Do not PGP sign your patch. Most likely, your maintainer or other people on the
267 list would not have your PGP key and would not bother obtaining it anyway.
268 Your patch is not judged by who you are; a good patch from an unknown origin
269 has a far better chance of being accepted than a patch from a known, respected
270 origin that is done poorly or does incorrect things.
271
272 If you really really really really want to do a PGP signed
273 patch, format it as "multipart/signed", not a text/plain message
274 that starts with `-----BEGIN PGP SIGNED MESSAGE-----`. That is
275 not a text/plain, it's something else.
276
277 :security-ml-ref: footnoteref:[security-ml]
278
279 As mentioned at the beginning of the section, patches that may be
280 security relevant should not be submitted to the public mailing list
281 mentioned below, but should instead be sent privately to the Git
282 Security mailing list{security-ml-ref}.
283
284 Send your patch with "To:" set to the mailing list, with "cc:" listing
285 people who are involved in the area you are touching (the `git
286 contacts` command in `contrib/contacts/` can help to
287 identify them), to solicit comments and reviews.
288
289 :current-maintainer: footnote:[The current maintainer: gitster@pobox.com]
290 :git-ml: footnote:[The mailing list: git@vger.kernel.org]
291
292 After the list reached a consensus that it is a good idea to apply the
293 patch, re-send it with "To:" set to the maintainer{current-maintainer} and "cc:" the
294 list{git-ml} for inclusion.
295
296 Do not forget to add trailers such as `Acked-by:`, `Reviewed-by:` and
297 `Tested-by:` lines as necessary to credit people who helped your
298 patch.
299
300 [[sign-off]]
301 === Certify your work by adding your `Signed-off-by` trailer
302
303 To improve tracking of who did what, we ask you to certify that you
304 wrote the patch or have the right to pass it on under the same license
305 as ours, by "signing off" your patch. Without sign-off, we cannot
306 accept your patches.
307
308 If you can certify the below D-C-O:
309
310 [[dco]]
311 .Developer's Certificate of Origin 1.1
312 ____
313 By making a contribution to this project, I certify that:
314
315 a. The contribution was created in whole or in part by me and I
316 have the right to submit it under the open source license
317 indicated in the file; or
318
319 b. The contribution is based upon previous work that, to the best
320 of my knowledge, is covered under an appropriate open source
321 license and I have the right under that license to submit that
322 work with modifications, whether created in whole or in part
323 by me, under the same open source license (unless I am
324 permitted to submit under a different license), as indicated
325 in the file; or
326
327 c. The contribution was provided directly to me by some other
328 person who certified (a), (b) or (c) and I have not modified
329 it.
330
331 d. I understand and agree that this project and the contribution
332 are public and that a record of the contribution (including all
333 personal information I submit with it, including my sign-off) is
334 maintained indefinitely and may be redistributed consistent with
335 this project or the open source license(s) involved.
336 ____
337
338 you add a "Signed-off-by" trailer to your commit, that looks like
339 this:
340
341 ....
342 Signed-off-by: Random J Developer <random@developer.example.org>
343 ....
344
345 This line can be added by Git if you run the git-commit command with
346 the -s option.
347
348 Notice that you can place your own `Signed-off-by` trailer when
349 forwarding somebody else's patch with the above rules for
350 D-C-O. Indeed you are encouraged to do so. Do not forget to
351 place an in-body "From: " line at the beginning to properly attribute
352 the change to its true author (see (2) above).
353
354 This procedure originally came from the Linux kernel project, so our
355 rule is quite similar to theirs, but what exactly it means to sign-off
356 your patch differs from project to project, so it may be different
357 from that of the project you are accustomed to.
358
359 [[real-name]]
360 Also notice that a real name is used in the `Signed-off-by` trailer. Please
361 don't hide your real name.
362
363 [[commit-trailers]]
364 If you like, you can put extra tags at the end:
365
366 . `Reported-by:` is used to credit someone who found the bug that
367 the patch attempts to fix.
368 . `Acked-by:` says that the person who is more familiar with the area
369 the patch attempts to modify liked the patch.
370 . `Reviewed-by:`, unlike the other tags, can only be offered by the
371 reviewer and means that she is completely satisfied that the patch
372 is ready for application. It is usually offered only after a
373 detailed review.
374 . `Tested-by:` is used to indicate that the person applied the patch
375 and found it to have the desired effect.
376
377 You can also create your own tag or use one that's in common usage
378 such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:".
379
380 == Subsystems with dedicated maintainers
381
382 Some parts of the system have dedicated maintainers with their own
383 repositories.
384
385 - `git-gui/` comes from git-gui project, maintained by Pratyush Yadav:
386
387 https://github.com/prati0100/git-gui.git
388
389 - `gitk-git/` comes from Paul Mackerras's gitk project:
390
391 git://ozlabs.org/~paulus/gitk
392
393 - `po/` comes from the localization coordinator, Jiang Xin:
394
395 https://github.com/git-l10n/git-po/
396
397 Patches to these parts should be based on their trees.
398
399 [[patch-flow]]
400 == An ideal patch flow
401
402 Here is an ideal patch flow for this project the current maintainer
403 suggests to the contributors:
404
405 . You come up with an itch. You code it up.
406
407 . Send it to the list and cc people who may need to know about
408 the change.
409 +
410 The people who may need to know are the ones whose code you
411 are butchering. These people happen to be the ones who are
412 most likely to be knowledgeable enough to help you, but
413 they have no obligation to help you (i.e. you ask for help,
414 don't demand). +git log -p {litdd} _$area_you_are_modifying_+ would
415 help you find out who they are.
416
417 . You get comments and suggestions for improvements. You may
418 even get them in an "on top of your change" patch form.
419
420 . Polish, refine, and re-send to the list and the people who
421 spend their time to improve your patch. Go back to step (2).
422
423 . The list forms consensus that the last round of your patch is
424 good. Send it to the maintainer and cc the list.
425
426 . A topic branch is created with the patch and is merged to `next`,
427 and cooked further and eventually graduates to `master`.
428
429 In any time between the (2)-(3) cycle, the maintainer may pick it up
430 from the list and queue it to `seen`, in order to make it easier for
431 people play with it without having to pick up and apply the patch to
432 their trees themselves.
433
434 [[patch-status]]
435 == Know the status of your patch after submission
436
437 * You can use Git itself to find out when your patch is merged in
438 master. `git pull --rebase` will automatically skip already-applied
439 patches, and will let you know. This works only if you rebase on top
440 of the branch in which your patch has been merged (i.e. it will not
441 tell you if your patch is merged in `seen` if you rebase on top of
442 master).
443
444 * Read the Git mailing list, the maintainer regularly posts messages
445 entitled "What's cooking in git.git" and "What's in git.git" giving
446 the status of various proposed changes.
447
448 [[travis]]
449 == GitHub-Travis CI hints
450
451 With an account at GitHub (you can get one for free to work on open
452 source projects), you can use Travis CI to test your changes on Linux,
453 Mac (and hopefully soon Windows). You can find a successful example
454 test build here: https://travis-ci.org/git/git/builds/120473209
455
456 Follow these steps for the initial setup:
457
458 . Fork https://github.com/git/git to your GitHub account.
459 You can find detailed instructions how to fork here:
460 https://help.github.com/articles/fork-a-repo/
461
462 . Open the Travis CI website: https://travis-ci.org
463
464 . Press the "Sign in with GitHub" button.
465
466 . Grant Travis CI permissions to access your GitHub account.
467 You can find more information about the required permissions here:
468 https://docs.travis-ci.com/user/github-oauth-scopes
469
470 . Open your Travis CI profile page: https://travis-ci.org/profile
471
472 . Enable Travis CI builds for your Git fork.
473
474 After the initial setup, Travis CI will run whenever you push new changes
475 to your fork of Git on GitHub. You can monitor the test state of all your
476 branches here: https://travis-ci.org/__<Your GitHub handle>__/git/branches
477
478 If a branch did not pass all test cases then it is marked with a red
479 cross. In that case you can click on the failing Travis CI job and
480 scroll all the way down in the log. Find the line "<-- Click here to see
481 detailed test output!" and click on the triangle next to the log line
482 number to expand the detailed test output. Here is such a failing
483 example: https://travis-ci.org/git/git/jobs/122676187
484
485 Fix the problem and push your fix to your Git fork. This will trigger
486 a new Travis CI build to ensure all tests pass.
487
488 [[mua]]
489 == MUA specific hints
490
491 Some of patches I receive or pick up from the list share common
492 patterns of breakage. Please make sure your MUA is set up
493 properly not to corrupt whitespaces.
494
495 See the DISCUSSION section of linkgit:git-format-patch[1] for hints on
496 checking your patch by mailing it to yourself and applying with
497 linkgit:git-am[1].
498
499 While you are at it, check the resulting commit log message from
500 a trial run of applying the patch. If what is in the resulting
501 commit is not exactly what you would want to see, it is very
502 likely that your maintainer would end up hand editing the log
503 message when he applies your patch. Things like "Hi, this is my
504 first patch.\n", if you really want to put in the patch e-mail,
505 should come after the three-dash line that signals the end of the
506 commit message.
507
508
509 === Pine
510
511 (Johannes Schindelin)
512
513 ....
514 I don't know how many people still use pine, but for those poor
515 souls it may be good to mention that the quell-flowed-text is
516 needed for recent versions.
517
518 ... the "no-strip-whitespace-before-send" option, too. AFAIK it
519 was introduced in 4.60.
520 ....
521
522 (Linus Torvalds)
523
524 ....
525 And 4.58 needs at least this.
526
527 diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1)
528 Author: Linus Torvalds <torvalds@g5.osdl.org>
529 Date: Mon Aug 15 17:23:51 2005 -0700
530
531 Fix pine whitespace-corruption bug
532
533 There's no excuse for unconditionally removing whitespace from
534 the pico buffers on close.
535
536 diff --git a/pico/pico.c b/pico/pico.c
537 --- a/pico/pico.c
538 +++ b/pico/pico.c
539 @@ -219,7 +219,9 @@ PICO *pm;
540 switch(pico_all_done){ /* prepare for/handle final events */
541 case COMP_EXIT : /* already confirmed */
542 packheader();
543 +#if 0
544 stripwhitespace();
545 +#endif
546 c |= COMP_EXIT;
547 break;
548 ....
549
550 (Daniel Barkalow)
551
552 ....
553 > A patch to SubmittingPatches, MUA specific help section for
554 > users of Pine 4.63 would be very much appreciated.
555
556 Ah, it looks like a recent version changed the default behavior to do the
557 right thing, and inverted the sense of the configuration option. (Either
558 that or Gentoo did it.) So you need to set the
559 "no-strip-whitespace-before-send" option, unless the option you have is
560 "strip-whitespace-before-send", in which case you should avoid checking
561 it.
562 ....
563
564 === Thunderbird, KMail, GMail
565
566 See the MUA-SPECIFIC HINTS section of linkgit:git-format-patch[1].
567
568 === Gnus
569
570 "|" in the `*Summary*` buffer can be used to pipe the current
571 message to an external program, and this is a handy way to drive
572 `git am`. However, if the message is MIME encoded, what is
573 piped into the program is the representation you see in your
574 `*Article*` buffer after unwrapping MIME. This is often not what
575 you would want for two reasons. It tends to screw up non ASCII
576 characters (most notably in people's names), and also
577 whitespaces (fatal in patches). Running "C-u g" to display the
578 message in raw form before using "|" to run the pipe can work
579 this problem around.