hashmap: adjust documentation to reflect reality
[git/git.git] / Documentation / SubmittingPatches
1 Here are some guidelines for people who want to contribute their code
2 to this software.
4 (0) Decide what to base your work on.
6 In general, always base your work on the oldest branch that your
7 change is relevant to.
9 - A bugfix should be based on 'maint' in general. If the bug is not
10 present in 'maint', base it on 'master'. For a bug that's not yet
11 in 'master', find the topic that introduces the regression, and
12 base your work on the tip of the topic.
14 - A new feature should be based on 'master' in general. If the new
15 feature depends on a topic that is in 'pu', but not in 'master',
16 base your work on the tip of that topic.
18 - Corrections and enhancements to a topic not yet in 'master' should
19 be based on the tip of that topic. If the topic has not been merged
20 to 'next', it's alright to add a note to squash minor corrections
21 into the series.
23 - In the exceptional case that a new feature depends on several topics
24 not in 'master', start working on 'next' or 'pu' privately and send
25 out patches for discussion. Before the final merge, you may have to
26 wait until some of the dependent topics graduate to 'master', and
27 rebase your work.
29 - Some parts of the system have dedicated maintainers with their own
30 repositories (see the section "Subsystems" below). Changes to
31 these parts should be based on their trees.
33 To find the tip of a topic branch, run "git log --first-parent
34 master..pu" and look for the merge commit. The second parent of this
35 commit is the tip of the topic branch.
37 (1) Make separate commits for logically separate changes.
39 Unless your patch is really trivial, you should not be sending
40 out a patch that was generated between your working tree and
41 your commit head. Instead, always make a commit with complete
42 commit message and generate a series of patches from your
43 repository. It is a good discipline.
45 Give an explanation for the change(s) that is detailed enough so
46 that people can judge if it is good thing to do, without reading
47 the actual patch text to determine how well the code does what
48 the explanation promises to do.
50 If your description starts to get too long, that's a sign that you
51 probably need to split up your commit to finer grained pieces.
52 That being said, patches which plainly describe the things that
53 help reviewers check the patch, and future maintainers understand
54 the code, are the most beautiful patches. Descriptions that summarize
55 the point in the subject well, and describe the motivation for the
56 change, the approach taken by the change, and if relevant how this
57 differs substantially from the prior version, are all good things
58 to have.
60 Make sure that you have tests for the bug you are fixing. See
61 t/README for guidance.
63 When adding a new feature, make sure that you have new tests to show
64 the feature triggers the new behavior when it should, and to show the
65 feature does not trigger when it shouldn't. After any code change, make
66 sure that the entire test suite passes.
68 If you have an account at GitHub (and you can get one for free to work
69 on open source projects), you can use their Travis CI integration to
70 test your changes on Linux, Mac (and hopefully soon Windows). See
71 GitHub-Travis CI hints section for details.
73 Do not forget to update the documentation to describe the updated
74 behavior and make sure that the resulting documentation set formats
75 well. It is currently a liberal mixture of US and UK English norms for
76 spelling and grammar, which is somewhat unfortunate. A huge patch that
77 touches the files all over the place only to correct the inconsistency
78 is not welcome, though. Potential clashes with other changes that can
79 result from such a patch are not worth it. We prefer to gradually
80 reconcile the inconsistencies in favor of US English, with small and
81 easily digestible patches, as a side effect of doing some other real
82 work in the vicinity (e.g. rewriting a paragraph for clarity, while
83 turning en_UK spelling to en_US). Obvious typographical fixes are much
84 more welcomed ("teh -> "the"), preferably submitted as independent
85 patches separate from other documentation changes.
87 Oh, another thing. We are picky about whitespaces. Make sure your
88 changes do not trigger errors with the sample pre-commit hook shipped
89 in templates/hooks--pre-commit. To help ensure this does not happen,
90 run "git diff --check" on your changes before you commit.
93 (2) Describe your changes well.
95 The first line of the commit message should be a short description (50
96 characters is the soft limit, see DISCUSSION in git-commit(1)), and
97 should skip the full stop. It is also conventional in most cases to
98 prefix the first line with "area: " where the area is a filename or
99 identifier for the general area of the code being modified, e.g.
101 . doc: clarify distinction between sign-off and pgp-signing
102 . githooks.txt: improve the intro section
104 If in doubt which identifier to use, run "git log --no-merges" on the
105 files you are modifying to see the current conventions.
107 It's customary to start the remainder of the first line after "area: "
108 with a lower-case letter. E.g. "doc: clarify...", not "doc:
109 Clarify...", or "githooks.txt: improve...", not "githooks.txt:
110 Improve...".
112 The body should provide a meaningful commit message, which:
114 . explains the problem the change tries to solve, i.e. what is wrong
115 with the current code without the change.
117 . justifies the way the change solves the problem, i.e. why the
118 result with the change is better.
120 . alternate solutions considered but discarded, if any.
122 Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
123 instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
124 to do frotz", as if you are giving orders to the codebase to change
125 its behavior. Try to make sure your explanation can be understood
126 without external resources. Instead of giving a URL to a mailing list
127 archive, summarize the relevant points of the discussion.
129 If you want to reference a previous commit in the history of a stable
130 branch, use the format "abbreviated sha1 (subject, date)",
131 with the subject enclosed in a pair of double-quotes, like this:
133 Commit f86a374 ("pack-bitmap.c: fix a memleak", 2015-03-30)
134 noticed that ...
136 The "Copy commit summary" command of gitk can be used to obtain this
137 format, or this invocation of "git show":
139 git show -s --date=short --pretty='format:%h ("%s", %ad)' <commit>
141 (3) Generate your patch using Git tools out of your commits.
143 Git based diff tools generate unidiff which is the preferred format.
145 You do not have to be afraid to use -M option to "git diff" or
146 "git format-patch", if your patch involves file renames. The
147 receiving end can handle them just fine.
149 Please make sure your patch does not add commented out debugging code,
150 or include any extra files which do not relate to what your patch
151 is trying to achieve. Make sure to review
152 your patch after generating it, to ensure accuracy. Before
153 sending out, please make sure it cleanly applies to the "master"
154 branch head. If you are preparing a work based on "next" branch,
155 that is fine, but please mark it as such.
158 (4) Sending your patches.
160 Learn to use format-patch and send-email if possible. These commands
161 are optimized for the workflow of sending patches, avoiding many ways
162 your existing e-mail client that is optimized for "multipart/*" mime
163 type e-mails to corrupt and render your patches unusable.
165 People on the Git mailing list need to be able to read and
166 comment on the changes you are submitting. It is important for
167 a developer to be able to "quote" your changes, using standard
168 e-mail tools, so that they may comment on specific portions of
169 your code. For this reason, each patch should be submitted
170 "inline" in a separate message.
172 Multiple related patches should be grouped into their own e-mail
173 thread to help readers find all parts of the series. To that end,
174 send them as replies to either an additional "cover letter" message
175 (see below), the first patch, or the respective preceding patch.
177 If your log message (including your name on the
178 Signed-off-by line) is not writable in ASCII, make sure that
179 you send off a message in the correct encoding.
181 WARNING: Be wary of your MUAs word-wrap
182 corrupting your patch. Do not cut-n-paste your patch; you can
183 lose tabs that way if you are not careful.
185 It is a common convention to prefix your subject line with
186 [PATCH]. This lets people easily distinguish patches from other
187 e-mail discussions. Use of markers in addition to PATCH within
188 the brackets to describe the nature of the patch is also
189 encouraged. E.g. [RFC PATCH] (where RFC stands for "request for
190 comments") is often used to indicate a patch needs further
191 discussion before being accepted, [PATCH v2], [PATCH v3] etc.
192 are often seen when you are sending an update to what you have
193 previously sent.
195 The "git format-patch" command follows the best current practice to
196 format the body of an e-mail message. At the beginning of the
197 patch should come your commit message, ending with the
198 Signed-off-by: lines, and a line that consists of three dashes,
199 followed by the diffstat information and the patch itself. If
200 you are forwarding a patch from somebody else, optionally, at
201 the beginning of the e-mail message just before the commit
202 message starts, you can put a "From: " line to name that person.
203 To change the default "[PATCH]" in the subject to "[<text>]", use
204 `git format-patch --subject-prefix=<text>`. As a shortcut, you
205 can use `--rfc` instead of `--subject-prefix="RFC PATCH"`, or
206 `-v <n>` instead of `--subject-prefix="PATCH v<n>"`.
208 You often want to add additional explanation about the patch,
209 other than the commit message itself. Place such "cover letter"
210 material between the three-dash line and the diffstat. For
211 patches requiring multiple iterations of review and discussion,
212 an explanation of changes between each iteration can be kept in
213 Git-notes and inserted automatically following the three-dash
214 line via `git format-patch --notes`.
216 Do not attach the patch as a MIME attachment, compressed or not.
217 Do not let your e-mail client send quoted-printable. Do not let
218 your e-mail client send format=flowed which would destroy
219 whitespaces in your patches. Many
220 popular e-mail applications will not always transmit a MIME
221 attachment as plain text, making it impossible to comment on
222 your code. A MIME attachment also takes a bit more time to
223 process. This does not decrease the likelihood of your
224 MIME-attached change being accepted, but it makes it more likely
225 that it will be postponed.
227 Exception: If your mailer is mangling patches then someone may ask
228 you to re-send them using MIME, that is OK.
230 Do not PGP sign your patch. Most likely, your maintainer or other people on the
231 list would not have your PGP key and would not bother obtaining it anyway.
232 Your patch is not judged by who you are; a good patch from an unknown origin
233 has a far better chance of being accepted than a patch from a known, respected
234 origin that is done poorly or does incorrect things.
236 If you really really really really want to do a PGP signed
237 patch, format it as "multipart/signed", not a text/plain message
238 that starts with '-----BEGIN PGP SIGNED MESSAGE-----'. That is
239 not a text/plain, it's something else.
241 Send your patch with "To:" set to the mailing list, with "cc:" listing
242 people who are involved in the area you are touching (the output from
243 "git blame $path" and "git shortlog --no-merges $path" would help to
244 identify them), to solicit comments and reviews.
246 After the list reached a consensus that it is a good idea to apply the
247 patch, re-send it with "To:" set to the maintainer [*1*] and "cc:" the
248 list [*2*] for inclusion.
250 Do not forget to add trailers such as "Acked-by:", "Reviewed-by:" and
251 "Tested-by:" lines as necessary to credit people who helped your
252 patch.
254 [Addresses]
255 *1* The current maintainer: gitster@pobox.com
256 *2* The mailing list: git@vger.kernel.org
259 (5) Certify your work by adding your "Signed-off-by: " line
261 To improve tracking of who did what, we've borrowed the
262 "sign-off" procedure from the Linux kernel project on patches
263 that are being emailed around. Although core Git is a lot
264 smaller project it is a good discipline to follow it.
266 The sign-off is a simple line at the end of the explanation for
267 the patch, which certifies that you wrote it or otherwise have
268 the right to pass it on as a open-source patch. The rules are
269 pretty simple: if you can certify the below D-C-O:
271 Developer's Certificate of Origin 1.1
273 By making a contribution to this project, I certify that:
275 (a) The contribution was created in whole or in part by me and I
276 have the right to submit it under the open source license
277 indicated in the file; or
279 (b) The contribution is based upon previous work that, to the best
280 of my knowledge, is covered under an appropriate open source
281 license and I have the right under that license to submit that
282 work with modifications, whether created in whole or in part
283 by me, under the same open source license (unless I am
284 permitted to submit under a different license), as indicated
285 in the file; or
287 (c) The contribution was provided directly to me by some other
288 person who certified (a), (b) or (c) and I have not modified
289 it.
291 (d) I understand and agree that this project and the contribution
292 are public and that a record of the contribution (including all
293 personal information I submit with it, including my sign-off) is
294 maintained indefinitely and may be redistributed consistent with
295 this project or the open source license(s) involved.
297 then you just add a line saying
299 Signed-off-by: Random J Developer <random@developer.example.org>
301 This line can be automatically added by Git if you run the git-commit
302 command with the -s option.
304 Notice that you can place your own Signed-off-by: line when
305 forwarding somebody else's patch with the above rules for
306 D-C-O. Indeed you are encouraged to do so. Do not forget to
307 place an in-body "From: " line at the beginning to properly attribute
308 the change to its true author (see (2) above).
310 Also notice that a real name is used in the Signed-off-by: line. Please
311 don't hide your real name.
313 If you like, you can put extra tags at the end:
315 1. "Reported-by:" is used to credit someone who found the bug that
316 the patch attempts to fix.
317 2. "Acked-by:" says that the person who is more familiar with the area
318 the patch attempts to modify liked the patch.
319 3. "Reviewed-by:", unlike the other tags, can only be offered by the
320 reviewer and means that she is completely satisfied that the patch
321 is ready for application. It is usually offered only after a
322 detailed review.
323 4. "Tested-by:" is used to indicate that the person applied the patch
324 and found it to have the desired effect.
326 You can also create your own tag or use one that's in common usage
327 such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:".
329 ------------------------------------------------
330 Subsystems with dedicated maintainers
332 Some parts of the system have dedicated maintainers with their own
333 repositories.
335 - git-gui/ comes from git-gui project, maintained by Pat Thoyts:
337 git://repo.or.cz/git-gui.git
339 - gitk-git/ comes from Paul Mackerras's gitk project:
341 git://ozlabs.org/~paulus/gitk
343 - po/ comes from the localization coordinator, Jiang Xin:
345 https://github.com/git-l10n/git-po/
347 Patches to these parts should be based on their trees.
349 ------------------------------------------------
350 An ideal patch flow
352 Here is an ideal patch flow for this project the current maintainer
353 suggests to the contributors:
355 (0) You come up with an itch. You code it up.
357 (1) Send it to the list and cc people who may need to know about
358 the change.
360 The people who may need to know are the ones whose code you
361 are butchering. These people happen to be the ones who are
362 most likely to be knowledgeable enough to help you, but
363 they have no obligation to help you (i.e. you ask for help,
364 don't demand). "git log -p -- $area_you_are_modifying" would
365 help you find out who they are.
367 (2) You get comments and suggestions for improvements. You may
368 even get them in a "on top of your change" patch form.
370 (3) Polish, refine, and re-send to the list and the people who
371 spend their time to improve your patch. Go back to step (2).
373 (4) The list forms consensus that the last round of your patch is
374 good. Send it to the maintainer and cc the list.
376 (5) A topic branch is created with the patch and is merged to 'next',
377 and cooked further and eventually graduates to 'master'.
379 In any time between the (2)-(3) cycle, the maintainer may pick it up
380 from the list and queue it to 'pu', in order to make it easier for
381 people play with it without having to pick up and apply the patch to
382 their trees themselves.
384 ------------------------------------------------
385 Know the status of your patch after submission
387 * You can use Git itself to find out when your patch is merged in
388 master. 'git pull --rebase' will automatically skip already-applied
389 patches, and will let you know. This works only if you rebase on top
390 of the branch in which your patch has been merged (i.e. it will not
391 tell you if your patch is merged in pu if you rebase on top of
392 master).
394 * Read the Git mailing list, the maintainer regularly posts messages
395 entitled "What's cooking in git.git" and "What's in git.git" giving
396 the status of various proposed changes.
398 --------------------------------------------------
399 GitHub-Travis CI hints
401 With an account at GitHub (you can get one for free to work on open
402 source projects), you can use Travis CI to test your changes on Linux,
403 Mac (and hopefully soon Windows). You can find a successful example
404 test build here: https://travis-ci.org/git/git/builds/120473209
406 Follow these steps for the initial setup:
408 (1) Fork https://github.com/git/git to your GitHub account.
409 You can find detailed instructions how to fork here:
410 https://help.github.com/articles/fork-a-repo/
412 (2) Open the Travis CI website: https://travis-ci.org
414 (3) Press the "Sign in with GitHub" button.
416 (4) Grant Travis CI permissions to access your GitHub account.
417 You can find more information about the required permissions here:
418 https://docs.travis-ci.com/user/github-oauth-scopes
420 (5) Open your Travis CI profile page: https://travis-ci.org/profile
422 (6) Enable Travis CI builds for your Git fork.
424 After the initial setup, Travis CI will run whenever you push new changes
425 to your fork of Git on GitHub. You can monitor the test state of all your
426 branches here: https://travis-ci.org/<Your GitHub handle>/git/branches
428 If a branch did not pass all test cases then it is marked with a red
429 cross. In that case you can click on the failing Travis CI job and
430 scroll all the way down in the log. Find the line "<-- Click here to see
431 detailed test output!" and click on the triangle next to the log line
432 number to expand the detailed test output. Here is such a failing
433 example: https://travis-ci.org/git/git/jobs/122676187
435 Fix the problem and push your fix to your Git fork. This will trigger
436 a new Travis CI build to ensure all tests pass.
439 ------------------------------------------------
440 MUA specific hints
442 Some of patches I receive or pick up from the list share common
443 patterns of breakage. Please make sure your MUA is set up
444 properly not to corrupt whitespaces.
446 See the DISCUSSION section of git-format-patch(1) for hints on
447 checking your patch by mailing it to yourself and applying with
448 git-am(1).
450 While you are at it, check the resulting commit log message from
451 a trial run of applying the patch. If what is in the resulting
452 commit is not exactly what you would want to see, it is very
453 likely that your maintainer would end up hand editing the log
454 message when he applies your patch. Things like "Hi, this is my
455 first patch.\n", if you really want to put in the patch e-mail,
456 should come after the three-dash line that signals the end of the
457 commit message.
460 Pine
461 ----
463 (Johannes Schindelin)
465 I don't know how many people still use pine, but for those poor
466 souls it may be good to mention that the quell-flowed-text is
467 needed for recent versions.
469 ... the "no-strip-whitespace-before-send" option, too. AFAIK it
470 was introduced in 4.60.
472 (Linus Torvalds)
474 And 4.58 needs at least this.
476 ---
477 diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1)
478 Author: Linus Torvalds <torvalds@g5.osdl.org>
479 Date: Mon Aug 15 17:23:51 2005 -0700
481 Fix pine whitespace-corruption bug
483 There's no excuse for unconditionally removing whitespace from
484 the pico buffers on close.
486 diff --git a/pico/pico.c b/pico/pico.c
487 --- a/pico/pico.c
488 +++ b/pico/pico.c
489 @@ -219,7 +219,9 @@ PICO *pm;
490 switch(pico_all_done){ /* prepare for/handle final events */
491 case COMP_EXIT : /* already confirmed */
492 packheader();
493 +#if 0
494 stripwhitespace();
495 +#endif
496 c |= COMP_EXIT;
497 break;
500 (Daniel Barkalow)
502 > A patch to SubmittingPatches, MUA specific help section for
503 > users of Pine 4.63 would be very much appreciated.
505 Ah, it looks like a recent version changed the default behavior to do the
506 right thing, and inverted the sense of the configuration option. (Either
507 that or Gentoo did it.) So you need to set the
508 "no-strip-whitespace-before-send" option, unless the option you have is
509 "strip-whitespace-before-send", in which case you should avoid checking
510 it.
513 Thunderbird, KMail, GMail
514 -------------------------
516 See the MUA-SPECIFIC HINTS section of git-format-patch(1).
518 Gnus
519 ----
521 '|' in the *Summary* buffer can be used to pipe the current
522 message to an external program, and this is a handy way to drive
523 "git am". However, if the message is MIME encoded, what is
524 piped into the program is the representation you see in your
525 *Article* buffer after unwrapping MIME. This is often not what
526 you would want for two reasons. It tends to screw up non ASCII
527 characters (most notably in people's names), and also
528 whitespaces (fatal in patches). Running 'C-u g' to display the
529 message in raw form before using '|' to run the pipe can work
530 this problem around.