1Submitting Patches 2================== 3 4== Guidelines 5 6Here are some guidelines for people who want to contribute their code 7to this software. 8 9[[base-branch]] 10=== Decide what to base your work on. 11 12In general, always base your work on the oldest branch that your 13change is relevant to. 14 15* A bugfix should be based on `maint` in general. If the bug is not 16 present in `maint`, base it on `master`. For a bug that's not yet 17 in `master`, find the topic that introduces the regression, and 18 base your work on the tip of the topic. 19 20* A new feature should be based on `master` in general. If the new 21 feature depends on a topic that is in `pu`, but not in `master`, 22 base your work on the tip of that topic. 23 24* Corrections and enhancements to a topic not yet in `master` should 25 be based on the tip of that topic. If the topic has not been merged 26 to `next`, it's alright to add a note to squash minor corrections 27 into the series. 28 29* In the exceptional case that a new feature depends on several topics 30 not in `master`, start working on `next` or `pu` privately and send 31 out patches for discussion. Before the final merge, you may have to 32 wait until some of the dependent topics graduate to `master`, and 33 rebase your work. 34 35* Some parts of the system have dedicated maintainers with their own 36 repositories (see the section "Subsystems" below). Changes to 37 these parts should be based on their trees. 38 39To find the tip of a topic branch, run `git log --first-parent 40master..pu` and look for the merge commit. The second parent of this 41commit is the tip of the topic branch. 42 43[[separate-commits]] 44=== Make separate commits for logically separate changes. 45 46Unless your patch is really trivial, you should not be sending 47out a patch that was generated between your working tree and 48your commit head. Instead, always make a commit with complete 49commit message and generate a series of patches from your 50repository. It is a good discipline. 51 52Give an explanation for the change(s) that is detailed enough so 53that people can judge if it is good thing to do, without reading 54the actual patch text to determine how well the code does what 55the explanation promises to do. 56 57If your description starts to get too long, that's a sign that you 58probably need to split up your commit to finer grained pieces. 59That being said, patches which plainly describe the things that 60help reviewers check the patch, and future maintainers understand 61the code, are the most beautiful patches. Descriptions that summarize 62the point in the subject well, and describe the motivation for the 63change, the approach taken by the change, and if relevant how this 64differs substantially from the prior version, are all good things 65to have. 66 67Make sure that you have tests for the bug you are fixing. See 68`t/README` for guidance. 69 70[[tests]] 71When adding a new feature, make sure that you have new tests to show 72the feature triggers the new behavior when it should, and to show the 73feature does not trigger when it shouldn't. After any code change, make 74sure that the entire test suite passes. 75 76If you have an account at GitHub (and you can get one for free to work 77on open source projects), you can use their Travis CI integration to 78test your changes on Linux, Mac (and hopefully soon Windows). See 79GitHub-Travis CI hints section for details. 80 81Do not forget to update the documentation to describe the updated 82behavior and make sure that the resulting documentation set formats 83well. It is currently a liberal mixture of US and UK English norms for 84spelling and grammar, which is somewhat unfortunate. A huge patch that 85touches the files all over the place only to correct the inconsistency 86is not welcome, though. Potential clashes with other changes that can 87result from such a patch are not worth it. We prefer to gradually 88reconcile the inconsistencies in favor of US English, with small and 89easily digestible patches, as a side effect of doing some other real 90work in the vicinity (e.g. rewriting a paragraph for clarity, while 91turning en_UK spelling to en_US). Obvious typographical fixes are much 92more welcomed ("teh -> "the"), preferably submitted as independent 93patches separate from other documentation changes. 94 95[[whitespace-check]] 96Oh, another thing. We are picky about whitespaces. Make sure your 97changes do not trigger errors with the sample pre-commit hook shipped 98in `templates/hooks--pre-commit`. To help ensure this does not happen, 99run `git diff --check` on your changes before you commit. 100 101[[describe-changes]] 102=== Describe your changes well. 103 104The first line of the commit message should be a short description (50 105characters is the soft limit, see DISCUSSION in linkgit:git-commit[1]), 106and should skip the full stop. It is also conventional in most cases to 107prefix the first line with "area: " where the area is a filename or 108identifier for the general area of the code being modified, e.g. 109 110* doc: clarify distinction between sign-off and pgp-signing 111* githooks.txt: improve the intro section 112 113If in doubt which identifier to use, run `git log --no-merges` on the 114files you are modifying to see the current conventions. 115 116[[summary-section]] 117It's customary to start the remainder of the first line after "area: " 118with a lower-case letter. E.g. "doc: clarify...", not "doc: 119Clarify...", or "githooks.txt: improve...", not "githooks.txt: 120Improve...". 121 122[[meaningful-message]] 123The body should provide a meaningful commit message, which: 124 125. explains the problem the change tries to solve, i.e. what is wrong 126 with the current code without the change. 127 128. justifies the way the change solves the problem, i.e. why the 129 result with the change is better. 130 131. alternate solutions considered but discarded, if any. 132 133[[imperative-mood]] 134Describe your changes in imperative mood, e.g. "make xyzzy do frotz" 135instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy 136to do frotz", as if you are giving orders to the codebase to change 137its behavior. Try to make sure your explanation can be understood 138without external resources. Instead of giving a URL to a mailing list 139archive, summarize the relevant points of the discussion. 140 141[[commit-reference]] 142If you want to reference a previous commit in the history of a stable 143branch, use the format "abbreviated sha1 (subject, date)", 144with the subject enclosed in a pair of double-quotes, like this: 145 146.... 147 Commit f86a374 ("pack-bitmap.c: fix a memleak", 2015-03-30) 148 noticed that ... 149.... 150 151The "Copy commit summary" command of gitk can be used to obtain this 152format, or this invocation of `git show`: 153 154.... 155 git show -s --date=short --pretty='format:%h ("%s", %ad)' <commit> 156.... 157 158[[git-tools]] 159=== Generate your patch using Git tools out of your commits. 160 161Git based diff tools generate unidiff which is the preferred format. 162 163You do not have to be afraid to use `-M` option to `git diff` or 164`git format-patch`, if your patch involves file renames. The 165receiving end can handle them just fine. 166 167[[review-patch]] 168Please make sure your patch does not add commented out debugging code, 169or include any extra files which do not relate to what your patch 170is trying to achieve. Make sure to review 171your patch after generating it, to ensure accuracy. Before 172sending out, please make sure it cleanly applies to the `master` 173branch head. If you are preparing a work based on "next" branch, 174that is fine, but please mark it as such. 175 176[[send-patches]] 177=== Sending your patches. 178 179Learn to use format-patch and send-email if possible. These commands 180are optimized for the workflow of sending patches, avoiding many ways 181your existing e-mail client that is optimized for "multipart/*" mime 182type e-mails to corrupt and render your patches unusable. 183 184People on the Git mailing list need to be able to read and 185comment on the changes you are submitting. It is important for 186a developer to be able to "quote" your changes, using standard 187e-mail tools, so that they may comment on specific portions of 188your code. For this reason, each patch should be submitted 189"inline" in a separate message. 190 191Multiple related patches should be grouped into their own e-mail 192thread to help readers find all parts of the series. To that end, 193send them as replies to either an additional "cover letter" message 194(see below), the first patch, or the respective preceding patch. 195 196If your log message (including your name on the 197Signed-off-by line) is not writable in ASCII, make sure that 198you send off a message in the correct encoding. 199 200WARNING: Be wary of your MUAs word-wrap 201corrupting your patch. Do not cut-n-paste your patch; you can 202lose tabs that way if you are not careful. 203 204It is a common convention to prefix your subject line with 205[PATCH]. This lets people easily distinguish patches from other 206e-mail discussions. Use of additional markers after PATCH and 207the closing bracket to mark the nature of the patch is also 208encouraged. E.g. [PATCH/RFC] is often used when the patch is 209not ready to be applied but it is for discussion, [PATCH v2], 210[PATCH v3] etc. are often seen when you are sending an update to 211what you have previously sent. 212 213`git format-patch` command follows the best current practice to 214format the body of an e-mail message. At the beginning of the 215patch should come your commit message, ending with the 216Signed-off-by: lines, and a line that consists of three dashes, 217followed by the diffstat information and the patch itself. If 218you are forwarding a patch from somebody else, optionally, at 219the beginning of the e-mail message just before the commit 220message starts, you can put a "From: " line to name that person. 221 222You often want to add additional explanation about the patch, 223other than the commit message itself. Place such "cover letter" 224material between the three-dash line and the diffstat. For 225patches requiring multiple iterations of review and discussion, 226an explanation of changes between each iteration can be kept in 227Git-notes and inserted automatically following the three-dash 228line via `git format-patch --notes`. 229 230[[attachment]] 231Do not attach the patch as a MIME attachment, compressed or not. 232Do not let your e-mail client send quoted-printable. Do not let 233your e-mail client send format=flowed which would destroy 234whitespaces in your patches. Many 235popular e-mail applications will not always transmit a MIME 236attachment as plain text, making it impossible to comment on 237your code. A MIME attachment also takes a bit more time to 238process. This does not decrease the likelihood of your 239MIME-attached change being accepted, but it makes it more likely 240that it will be postponed. 241 242Exception: If your mailer is mangling patches then someone may ask 243you to re-send them using MIME, that is OK. 244 245[[pgp-signature]] 246Do not PGP sign your patch. Most likely, your maintainer or other people on the 247list would not have your PGP key and would not bother obtaining it anyway. 248Your patch is not judged by who you are; a good patch from an unknown origin 249has a far better chance of being accepted than a patch from a known, respected 250origin that is done poorly or does incorrect things. 251 252If you really really really really want to do a PGP signed 253patch, format it as "multipart/signed", not a text/plain message 254that starts with `-----BEGIN PGP SIGNED MESSAGE-----`. That is 255not a text/plain, it's something else. 256 257Send your patch with "To:" set to the mailing list, with "cc:" listing 258people who are involved in the area you are touching (the output from 259+git blame _$path_+ and +git shortlog {litdd}no-merges _$path_+ would help to 260identify them), to solicit comments and reviews. 261 262:1: footnote:[The current maintainer: gitster@pobox.com] 263:2: footnote:[The mailing list: git@vger.kernel.org] 264 265After the list reached a consensus that it is a good idea to apply the 266patch, re-send it with "To:" set to the maintainer{1} and "cc:" the 267list{2} for inclusion. 268 269Do not forget to add trailers such as `Acked-by:`, `Reviewed-by:` and 270`Tested-by:` lines as necessary to credit people who helped your 271patch. 272 273[[sign-off]] 274=== Certify your work by adding your "Signed-off-by: " line 275 276To improve tracking of who did what, we've borrowed the 277"sign-off" procedure from the Linux kernel project on patches 278that are being emailed around. Although core Git is a lot 279smaller project it is a good discipline to follow it. 280 281The sign-off is a simple line at the end of the explanation for 282the patch, which certifies that you wrote it or otherwise have 283the right to pass it on as a open-source patch. The rules are 284pretty simple: if you can certify the below D-C-O: 285 286[[dco]] 287.Developer's Certificate of Origin 1.1 288____ 289By making a contribution to this project, I certify that: 290 291a. The contribution was created in whole or in part by me and I 292 have the right to submit it under the open source license 293 indicated in the file; or 294 295b. The contribution is based upon previous work that, to the best 296 of my knowledge, is covered under an appropriate open source 297 license and I have the right under that license to submit that 298 work with modifications, whether created in whole or in part 299 by me, under the same open source license (unless I am 300 permitted to submit under a different license), as indicated 301 in the file; or 302 303c. The contribution was provided directly to me by some other 304 person who certified (a), (b) or (c) and I have not modified 305 it. 306 307d. I understand and agree that this project and the contribution 308 are public and that a record of the contribution (including all 309 personal information I submit with it, including my sign-off) is 310 maintained indefinitely and may be redistributed consistent with 311 this project or the open source license(s) involved. 312____ 313 314then you just add a line saying 315 316.... 317 Signed-off-by: Random J Developer <random@developer.example.org> 318.... 319 320This line can be automatically added by Git if you run the git-commit 321command with the -s option. 322 323Notice that you can place your own Signed-off-by: line when 324forwarding somebody else's patch with the above rules for 325D-C-O. Indeed you are encouraged to do so. Do not forget to 326place an in-body "From: " line at the beginning to properly attribute 327the change to its true author (see (2) above). 328 329[[real-name]] 330Also notice that a real name is used in the Signed-off-by: line. Please 331don't hide your real name. 332 333[[commit-trailers]] 334If you like, you can put extra tags at the end: 335 336. `Reported-by:` is used to credit someone who found the bug that 337 the patch attempts to fix. 338. `Acked-by:` says that the person who is more familiar with the area 339 the patch attempts to modify liked the patch. 340. `Reviewed-by:`, unlike the other tags, can only be offered by the 341 reviewer and means that she is completely satisfied that the patch 342 is ready for application. It is usually offered only after a 343 detailed review. 344. `Tested-by:` is used to indicate that the person applied the patch 345 and found it to have the desired effect. 346 347You can also create your own tag or use one that's in common usage 348such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:". 349 350== Subsystems with dedicated maintainers 351 352Some parts of the system have dedicated maintainers with their own 353repositories. 354 355- 'git-gui/' comes from git-gui project, maintained by Pat Thoyts: 356 357 git://repo.or.cz/git-gui.git 358 359- 'gitk-git/' comes from Paul Mackerras's gitk project: 360 361 git://ozlabs.org/~paulus/gitk 362 363- 'po/' comes from the localization coordinator, Jiang Xin: 364 365 https://github.com/git-l10n/git-po/ 366 367Patches to these parts should be based on their trees. 368 369[[patch-flow]] 370== An ideal patch flow 371 372Here is an ideal patch flow for this project the current maintainer 373suggests to the contributors: 374 375. You come up with an itch. You code it up. 376 377. Send it to the list and cc people who may need to know about 378 the change. 379+ 380The people who may need to know are the ones whose code you 381are butchering. These people happen to be the ones who are 382most likely to be knowledgeable enough to help you, but 383they have no obligation to help you (i.e. you ask for help, 384don't demand). +git log -p {litdd} _$area_you_are_modifying_+ would 385help you find out who they are. 386 387. You get comments and suggestions for improvements. You may 388 even get them in a "on top of your change" patch form. 389 390. Polish, refine, and re-send to the list and the people who 391 spend their time to improve your patch. Go back to step (2). 392 393. The list forms consensus that the last round of your patch is 394 good. Send it to the maintainer and cc the list. 395 396. A topic branch is created with the patch and is merged to `next`, 397 and cooked further and eventually graduates to `master`. 398 399In any time between the (2)-(3) cycle, the maintainer may pick it up 400from the list and queue it to `pu`, in order to make it easier for 401people play with it without having to pick up and apply the patch to 402their trees themselves. 403 404[[patch-status]] 405== Know the status of your patch after submission 406 407* You can use Git itself to find out when your patch is merged in 408 master. `git pull --rebase` will automatically skip already-applied 409 patches, and will let you know. This works only if you rebase on top 410 of the branch in which your patch has been merged (i.e. it will not 411 tell you if your patch is merged in pu if you rebase on top of 412 master). 413 414* Read the Git mailing list, the maintainer regularly posts messages 415 entitled "What's cooking in git.git" and "What's in git.git" giving 416 the status of various proposed changes. 417 418[[travis]] 419== GitHub-Travis CI hints 420 421With an account at GitHub (you can get one for free to work on open 422source projects), you can use Travis CI to test your changes on Linux, 423Mac (and hopefully soon Windows). You can find a successful example 424test build here: https://travis-ci.org/git/git/builds/120473209 425 426Follow these steps for the initial setup: 427 428. Fork https://github.com/git/git to your GitHub account. 429 You can find detailed instructions how to fork here: 430 https://help.github.com/articles/fork-a-repo/ 431 432. Open the Travis CI website: https://travis-ci.org 433 434. Press the "Sign in with GitHub" button. 435 436. Grant Travis CI permissions to access your GitHub account. 437 You can find more information about the required permissions here: 438 https://docs.travis-ci.com/user/github-oauth-scopes 439 440. Open your Travis CI profile page: https://travis-ci.org/profile 441 442. Enable Travis CI builds for your Git fork. 443 444After the initial setup, Travis CI will run whenever you push new changes 445to your fork of Git on GitHub. You can monitor the test state of all your 446branches here: https://travis-ci.org/__<Your GitHub handle>__/git/branches 447 448If a branch did not pass all test cases then it is marked with a red 449cross. In that case you can click on the failing Travis CI job and 450scroll all the way down in the log. Find the line "<-- Click here to see 451detailed test output!" and click on the triangle next to the log line 452number to expand the detailed test output. Here is such a failing 453example: https://travis-ci.org/git/git/jobs/122676187 454 455Fix the problem and push your fix to your Git fork. This will trigger 456a new Travis CI build to ensure all tests pass. 457 458[[mua]] 459== MUA specific hints 460 461Some of patches I receive or pick up from the list share common 462patterns of breakage. Please make sure your MUA is set up 463properly not to corrupt whitespaces. 464 465See the DISCUSSION section of linkgit:git-format-patch[1] for hints on 466checking your patch by mailing it to yourself and applying with 467linkgit:git-am[1]. 468 469While you are at it, check the resulting commit log message from 470a trial run of applying the patch. If what is in the resulting 471commit is not exactly what you would want to see, it is very 472likely that your maintainer would end up hand editing the log 473message when he applies your patch. Things like "Hi, this is my 474first patch.\n", if you really want to put in the patch e-mail, 475should come after the three-dash line that signals the end of the 476commit message. 477 478 479=== Pine 480 481(Johannes Schindelin) 482 483.... 484I don't know how many people still use pine, but for those poor 485souls it may be good to mention that the quell-flowed-text is 486needed for recent versions. 487 488... the "no-strip-whitespace-before-send" option, too. AFAIK it 489was introduced in 4.60. 490.... 491 492(Linus Torvalds) 493 494.... 495And 4.58 needs at least this. 496 497diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1) 498Author: Linus Torvalds <torvalds@g5.osdl.org> 499Date: Mon Aug 15 17:23:51 2005 -0700 500 501 Fix pine whitespace-corruption bug 502 503 There's no excuse for unconditionally removing whitespace from 504 the pico buffers on close. 505 506diff --git a/pico/pico.c b/pico/pico.c 507--- a/pico/pico.c 508+++ b/pico/pico.c 509@@ -219,7 +219,9 @@ PICO *pm; 510 switch(pico_all_done){ /* prepare for/handle final events */ 511 case COMP_EXIT : /* already confirmed */ 512 packheader(); 513+#if 0 514 stripwhitespace(); 515+#endif 516 c |= COMP_EXIT; 517 break; 518.... 519 520(Daniel Barkalow) 521 522.... 523> A patch to SubmittingPatches, MUA specific help section for 524> users of Pine 4.63 would be very much appreciated. 525 526Ah, it looks like a recent version changed the default behavior to do the 527right thing, and inverted the sense of the configuration option. (Either 528that or Gentoo did it.) So you need to set the 529"no-strip-whitespace-before-send" option, unless the option you have is 530"strip-whitespace-before-send", in which case you should avoid checking 531it. 532.... 533 534=== Thunderbird, KMail, GMail 535 536See the MUA-SPECIFIC HINTS section of linkgit:git-format-patch[1]. 537 538=== Gnus 539 540"|" in the `*Summary*` buffer can be used to pipe the current 541message to an external program, and this is a handy way to drive 542`git am`. However, if the message is MIME encoded, what is 543piped into the program is the representation you see in your 544`*Article*` buffer after unwrapping MIME. This is often not what 545you would want for two reasons. It tends to screw up non ASCII 546characters (most notably in people's names), and also 547whitespaces (fatal in patches). Running "C-u g" to display the 548message in raw form before using "|" to run the pipe can work 549this problem around.