Documentation / SubmittingPatcheson commit Merge branch 'jc/fetch-refspec-doc-update' into maint (9fc7bc6)
   1Here are some guidelines for people who want to contribute their code
   2to this software.
   3
   4(0) Decide what to base your work on.
   5
   6In general, always base your work on the oldest branch that your
   7change is relevant to.
   8
   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.
  13
  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.
  17
  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.
  22
  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.
  28
  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.
  32
  33To find the tip of a topic branch, run "git log --first-parent
  34master..pu" and look for the merge commit. The second parent of this
  35commit is the tip of the topic branch.
  36
  37(1) Make separate commits for logically separate changes.
  38
  39Unless your patch is really trivial, you should not be sending
  40out a patch that was generated between your working tree and
  41your commit head.  Instead, always make a commit with complete
  42commit message and generate a series of patches from your
  43repository.  It is a good discipline.
  44
  45Give an explanation for the change(s) that is detailed enough so
  46that people can judge if it is good thing to do, without reading
  47the actual patch text to determine how well the code does what
  48the explanation promises to do.
  49
  50If your description starts to get too long, that's a sign that you
  51probably need to split up your commit to finer grained pieces.
  52That being said, patches which plainly describe the things that
  53help reviewers check the patch, and future maintainers understand
  54the code, are the most beautiful patches.  Descriptions that summarize
  55the point in the subject well, and describe the motivation for the
  56change, the approach taken by the change, and if relevant how this
  57differs substantially from the prior version, are all good things
  58to have.
  59
  60Make sure that you have tests for the bug you are fixing.  See
  61t/README for guidance.
  62
  63When adding a new feature, make sure that you have new tests to show
  64the feature triggers the new behavior when it should, and to show the
  65feature does not trigger when it shouldn't.  After any code change, make
  66sure that the entire test suite passes.
  67
  68If you have an account at GitHub (and you can get one for free to work
  69on open source projects), you can use their Travis CI integration to
  70test your changes on Linux, Mac (and hopefully soon Windows).  See
  71GitHub-Travis CI hints section for details.
  72
  73Do not forget to update the documentation to describe the updated
  74behavior and make sure that the resulting documentation set formats
  75well. It is currently a liberal mixture of US and UK English norms for
  76spelling and grammar, which is somewhat unfortunate.  A huge patch that
  77touches the files all over the place only to correct the inconsistency
  78is not welcome, though.  Potential clashes with other changes that can
  79result from such a patch are not worth it.  We prefer to gradually
  80reconcile the inconsistencies in favor of US English, with small and
  81easily digestible patches, as a side effect of doing some other real
  82work in the vicinity (e.g. rewriting a paragraph for clarity, while
  83turning en_UK spelling to en_US).  Obvious typographical fixes are much
  84more welcomed ("teh -> "the"), preferably submitted as independent
  85patches separate from other documentation changes.
  86
  87Oh, another thing.  We are picky about whitespaces.  Make sure your
  88changes do not trigger errors with the sample pre-commit hook shipped
  89in templates/hooks--pre-commit.  To help ensure this does not happen,
  90run "git diff --check" on your changes before you commit.
  91
  92
  93(2) Describe your changes well.
  94
  95The first line of the commit message should be a short description (50
  96characters is the soft limit, see DISCUSSION in git-commit(1)), and
  97should skip the full stop.  It is also conventional in most cases to
  98prefix the first line with "area: " where the area is a filename or
  99identifier for the general area of the code being modified, e.g.
 100
 101  . doc: clarify distinction between sign-off and pgp-signing
 102  . githooks.txt: improve the intro section
 103
 104If in doubt which identifier to use, run "git log --no-merges" on the
 105files you are modifying to see the current conventions.
 106
 107It's customary to start the remainder of the first line after "area: "
 108with a lower-case letter. E.g. "doc: clarify...", not "doc:
 109Clarify...", or "githooks.txt: improve...", not "githooks.txt:
 110Improve...".
 111
 112The body should provide a meaningful commit message, which:
 113
 114  . explains the problem the change tries to solve, i.e. what is wrong
 115    with the current code without the change.
 116
 117  . justifies the way the change solves the problem, i.e. why the
 118    result with the change is better.
 119
 120  . alternate solutions considered but discarded, if any.
 121
 122Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
 123instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
 124to do frotz", as if you are giving orders to the codebase to change
 125its behavior.  Try to make sure your explanation can be understood
 126without external resources. Instead of giving a URL to a mailing list
 127archive, summarize the relevant points of the discussion.
 128
 129If you want to reference a previous commit in the history of a stable
 130branch, use the format "abbreviated sha1 (subject, date)",
 131with the subject enclosed in a pair of double-quotes, like this:
 132
 133    Commit f86a374 ("pack-bitmap.c: fix a memleak", 2015-03-30)
 134    noticed that ...
 135
 136The "Copy commit summary" command of gitk can be used to obtain this
 137format, or this invocation of "git show":
 138
 139    git show -s --date=short --pretty='format:%h ("%s", %ad)' <commit>
 140
 141(3) Generate your patch using Git tools out of your commits.
 142
 143Git based diff tools generate unidiff which is the preferred format.
 144
 145You 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
 147receiving end can handle them just fine.
 148
 149Please make sure your patch does not add commented out debugging code,
 150or include any extra files which do not relate to what your patch
 151is trying to achieve. Make sure to review
 152your patch after generating it, to ensure accuracy.  Before
 153sending out, please make sure it cleanly applies to the "master"
 154branch head.  If you are preparing a work based on "next" branch,
 155that is fine, but please mark it as such.
 156
 157
 158(4) Sending your patches.
 159
 160Learn to use format-patch and send-email if possible.  These commands
 161are optimized for the workflow of sending patches, avoiding many ways
 162your existing e-mail client that is optimized for "multipart/*" mime
 163type e-mails to corrupt and render your patches unusable.
 164
 165People on the Git mailing list need to be able to read and
 166comment on the changes you are submitting.  It is important for
 167a developer to be able to "quote" your changes, using standard
 168e-mail tools, so that they may comment on specific portions of
 169your code.  For this reason, each patch should be submitted
 170"inline" in a separate message.
 171
 172Multiple related patches should be grouped into their own e-mail
 173thread to help readers find all parts of the series.  To that end,
 174send them as replies to either an additional "cover letter" message
 175(see below), the first patch, or the respective preceding patch.
 176
 177If your log message (including your name on the
 178Signed-off-by line) is not writable in ASCII, make sure that
 179you send off a message in the correct encoding.
 180
 181WARNING: Be wary of your MUAs word-wrap
 182corrupting your patch.  Do not cut-n-paste your patch; you can
 183lose tabs that way if you are not careful.
 184
 185It is a common convention to prefix your subject line with
 186[PATCH].  This lets people easily distinguish patches from other
 187e-mail discussions.  Use of additional markers after PATCH and
 188the closing bracket to mark the nature of the patch is also
 189encouraged.  E.g. [PATCH/RFC] is often used when the patch is
 190not ready to be applied but it is for discussion, [PATCH v2],
 191[PATCH v3] etc. are often seen when you are sending an update to
 192what you have previously sent.
 193
 194"git format-patch" command follows the best current practice to
 195format the body of an e-mail message.  At the beginning of the
 196patch should come your commit message, ending with the
 197Signed-off-by: lines, and a line that consists of three dashes,
 198followed by the diffstat information and the patch itself.  If
 199you are forwarding a patch from somebody else, optionally, at
 200the beginning of the e-mail message just before the commit
 201message starts, you can put a "From: " line to name that person.
 202
 203You often want to add additional explanation about the patch,
 204other than the commit message itself.  Place such "cover letter"
 205material between the three-dash line and the diffstat.  For
 206patches requiring multiple iterations of review and discussion,
 207an explanation of changes between each iteration can be kept in
 208Git-notes and inserted automatically following the three-dash
 209line via `git format-patch --notes`.
 210
 211Do not attach the patch as a MIME attachment, compressed or not.
 212Do not let your e-mail client send quoted-printable.  Do not let
 213your e-mail client send format=flowed which would destroy
 214whitespaces in your patches. Many
 215popular e-mail applications will not always transmit a MIME
 216attachment as plain text, making it impossible to comment on
 217your code.  A MIME attachment also takes a bit more time to
 218process.  This does not decrease the likelihood of your
 219MIME-attached change being accepted, but it makes it more likely
 220that it will be postponed.
 221
 222Exception:  If your mailer is mangling patches then someone may ask
 223you to re-send them using MIME, that is OK.
 224
 225Do not PGP sign your patch. Most likely, your maintainer or other people on the
 226list would not have your PGP key and would not bother obtaining it anyway.
 227Your patch is not judged by who you are; a good patch from an unknown origin
 228has a far better chance of being accepted than a patch from a known, respected
 229origin that is done poorly or does incorrect things.
 230
 231If you really really really really want to do a PGP signed
 232patch, format it as "multipart/signed", not a text/plain message
 233that starts with '-----BEGIN PGP SIGNED MESSAGE-----'.  That is
 234not a text/plain, it's something else.
 235
 236Send your patch with "To:" set to the mailing list, with "cc:" listing
 237people who are involved in the area you are touching (the output from
 238"git blame $path" and "git shortlog --no-merges $path" would help to
 239identify them), to solicit comments and reviews.
 240
 241After the list reached a consensus that it is a good idea to apply the
 242patch, re-send it with "To:" set to the maintainer [*1*] and "cc:" the
 243list [*2*] for inclusion.
 244
 245Do not forget to add trailers such as "Acked-by:", "Reviewed-by:" and
 246"Tested-by:" lines as necessary to credit people who helped your
 247patch.
 248
 249    [Addresses]
 250     *1* The current maintainer: gitster@pobox.com
 251     *2* The mailing list: git@vger.kernel.org
 252
 253
 254(5) Certify your work by adding your "Signed-off-by: " line
 255
 256To improve tracking of who did what, we've borrowed the
 257"sign-off" procedure from the Linux kernel project on patches
 258that are being emailed around.  Although core Git is a lot
 259smaller project it is a good discipline to follow it.
 260
 261The sign-off is a simple line at the end of the explanation for
 262the patch, which certifies that you wrote it or otherwise have
 263the right to pass it on as a open-source patch.  The rules are
 264pretty simple: if you can certify the below D-C-O:
 265
 266        Developer's Certificate of Origin 1.1
 267
 268        By making a contribution to this project, I certify that:
 269
 270        (a) The contribution was created in whole or in part by me and I
 271            have the right to submit it under the open source license
 272            indicated in the file; or
 273
 274        (b) The contribution is based upon previous work that, to the best
 275            of my knowledge, is covered under an appropriate open source
 276            license and I have the right under that license to submit that
 277            work with modifications, whether created in whole or in part
 278            by me, under the same open source license (unless I am
 279            permitted to submit under a different license), as indicated
 280            in the file; or
 281
 282        (c) The contribution was provided directly to me by some other
 283            person who certified (a), (b) or (c) and I have not modified
 284            it.
 285
 286        (d) I understand and agree that this project and the contribution
 287            are public and that a record of the contribution (including all
 288            personal information I submit with it, including my sign-off) is
 289            maintained indefinitely and may be redistributed consistent with
 290            this project or the open source license(s) involved.
 291
 292then you just add a line saying
 293
 294        Signed-off-by: Random J Developer <random@developer.example.org>
 295
 296This line can be automatically added by Git if you run the git-commit
 297command with the -s option.
 298
 299Notice that you can place your own Signed-off-by: line when
 300forwarding somebody else's patch with the above rules for
 301D-C-O.  Indeed you are encouraged to do so.  Do not forget to
 302place an in-body "From: " line at the beginning to properly attribute
 303the change to its true author (see (2) above).
 304
 305Also notice that a real name is used in the Signed-off-by: line. Please
 306don't hide your real name.
 307
 308If you like, you can put extra tags at the end:
 309
 3101. "Reported-by:" is used to credit someone who found the bug that
 311   the patch attempts to fix.
 3122. "Acked-by:" says that the person who is more familiar with the area
 313   the patch attempts to modify liked the patch.
 3143. "Reviewed-by:", unlike the other tags, can only be offered by the
 315   reviewer and means that she is completely satisfied that the patch
 316   is ready for application.  It is usually offered only after a
 317   detailed review.
 3184. "Tested-by:" is used to indicate that the person applied the patch
 319   and found it to have the desired effect.
 320
 321You can also create your own tag or use one that's in common usage
 322such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:".
 323
 324------------------------------------------------
 325Subsystems with dedicated maintainers
 326
 327Some parts of the system have dedicated maintainers with their own
 328repositories.
 329
 330 - git-gui/ comes from git-gui project, maintained by Pat Thoyts:
 331
 332        git://repo.or.cz/git-gui.git
 333
 334 - gitk-git/ comes from Paul Mackerras's gitk project:
 335
 336        git://ozlabs.org/~paulus/gitk
 337
 338 - po/ comes from the localization coordinator, Jiang Xin:
 339
 340        https://github.com/git-l10n/git-po/
 341
 342Patches to these parts should be based on their trees.
 343
 344------------------------------------------------
 345An ideal patch flow
 346
 347Here is an ideal patch flow for this project the current maintainer
 348suggests to the contributors:
 349
 350 (0) You come up with an itch.  You code it up.
 351
 352 (1) Send it to the list and cc people who may need to know about
 353     the change.
 354
 355     The people who may need to know are the ones whose code you
 356     are butchering.  These people happen to be the ones who are
 357     most likely to be knowledgeable enough to help you, but
 358     they have no obligation to help you (i.e. you ask for help,
 359     don't demand).  "git log -p -- $area_you_are_modifying" would
 360     help you find out who they are.
 361
 362 (2) You get comments and suggestions for improvements.  You may
 363     even get them in a "on top of your change" patch form.
 364
 365 (3) Polish, refine, and re-send to the list and the people who
 366     spend their time to improve your patch.  Go back to step (2).
 367
 368 (4) The list forms consensus that the last round of your patch is
 369     good.  Send it to the maintainer and cc the list.
 370
 371 (5) A topic branch is created with the patch and is merged to 'next',
 372     and cooked further and eventually graduates to 'master'.
 373
 374In any time between the (2)-(3) cycle, the maintainer may pick it up
 375from the list and queue it to 'pu', in order to make it easier for
 376people play with it without having to pick up and apply the patch to
 377their trees themselves.
 378
 379------------------------------------------------
 380Know the status of your patch after submission
 381
 382* You can use Git itself to find out when your patch is merged in
 383  master. 'git pull --rebase' will automatically skip already-applied
 384  patches, and will let you know. This works only if you rebase on top
 385  of the branch in which your patch has been merged (i.e. it will not
 386  tell you if your patch is merged in pu if you rebase on top of
 387  master).
 388
 389* Read the Git mailing list, the maintainer regularly posts messages
 390  entitled "What's cooking in git.git" and "What's in git.git" giving
 391  the status of various proposed changes.
 392
 393--------------------------------------------------
 394GitHub-Travis CI hints
 395
 396With an account at GitHub (you can get one for free to work on open
 397source projects), you can use Travis CI to test your changes on Linux,
 398Mac (and hopefully soon Windows).  You can find a successful example
 399test build here: https://travis-ci.org/git/git/builds/120473209
 400
 401Follow these steps for the initial setup:
 402
 403 (1) Fork https://github.com/git/git to your GitHub account.
 404     You can find detailed instructions how to fork here:
 405     https://help.github.com/articles/fork-a-repo/
 406
 407 (2) Open the Travis CI website: https://travis-ci.org
 408
 409 (3) Press the "Sign in with GitHub" button.
 410
 411 (4) Grant Travis CI permissions to access your GitHub account.
 412     You can find more information about the required permissions here:
 413     https://docs.travis-ci.com/user/github-oauth-scopes
 414
 415 (5) Open your Travis CI profile page: https://travis-ci.org/profile
 416
 417 (6) Enable Travis CI builds for your Git fork.
 418
 419After the initial setup, Travis CI will run whenever you push new changes
 420to your fork of Git on GitHub.  You can monitor the test state of all your
 421branches here: https://travis-ci.org/<Your GitHub handle>/git/branches
 422
 423If a branch did not pass all test cases then it is marked with a red
 424cross.  In that case you can click on the failing Travis CI job and
 425scroll all the way down in the log.  Find the line "<-- Click here to see
 426detailed test output!" and click on the triangle next to the log line
 427number to expand the detailed test output.  Here is such a failing
 428example: https://travis-ci.org/git/git/jobs/122676187
 429
 430Fix the problem and push your fix to your Git fork.  This will trigger
 431a new Travis CI build to ensure all tests pass.
 432
 433
 434------------------------------------------------
 435MUA specific hints
 436
 437Some of patches I receive or pick up from the list share common
 438patterns of breakage.  Please make sure your MUA is set up
 439properly not to corrupt whitespaces.
 440
 441See the DISCUSSION section of git-format-patch(1) for hints on
 442checking your patch by mailing it to yourself and applying with
 443git-am(1).
 444
 445While you are at it, check the resulting commit log message from
 446a trial run of applying the patch.  If what is in the resulting
 447commit is not exactly what you would want to see, it is very
 448likely that your maintainer would end up hand editing the log
 449message when he applies your patch.  Things like "Hi, this is my
 450first patch.\n", if you really want to put in the patch e-mail,
 451should come after the three-dash line that signals the end of the
 452commit message.
 453
 454
 455Pine
 456----
 457
 458(Johannes Schindelin)
 459
 460I don't know how many people still use pine, but for those poor
 461souls it may be good to mention that the quell-flowed-text is
 462needed for recent versions.
 463
 464... the "no-strip-whitespace-before-send" option, too. AFAIK it
 465was introduced in 4.60.
 466
 467(Linus Torvalds)
 468
 469And 4.58 needs at least this.
 470
 471---
 472diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1)
 473Author: Linus Torvalds <torvalds@g5.osdl.org>
 474Date:   Mon Aug 15 17:23:51 2005 -0700
 475
 476    Fix pine whitespace-corruption bug
 477
 478    There's no excuse for unconditionally removing whitespace from
 479    the pico buffers on close.
 480
 481diff --git a/pico/pico.c b/pico/pico.c
 482--- a/pico/pico.c
 483+++ b/pico/pico.c
 484@@ -219,7 +219,9 @@ PICO *pm;
 485            switch(pico_all_done){      /* prepare for/handle final events */
 486              case COMP_EXIT :          /* already confirmed */
 487                packheader();
 488+#if 0
 489                stripwhitespace();
 490+#endif
 491                c |= COMP_EXIT;
 492                break;
 493
 494
 495(Daniel Barkalow)
 496
 497> A patch to SubmittingPatches, MUA specific help section for
 498> users of Pine 4.63 would be very much appreciated.
 499
 500Ah, it looks like a recent version changed the default behavior to do the
 501right thing, and inverted the sense of the configuration option. (Either
 502that or Gentoo did it.) So you need to set the
 503"no-strip-whitespace-before-send" option, unless the option you have is
 504"strip-whitespace-before-send", in which case you should avoid checking
 505it.
 506
 507
 508Thunderbird, KMail, GMail
 509-------------------------
 510
 511See the MUA-SPECIFIC HINTS section of git-format-patch(1).
 512
 513Gnus
 514----
 515
 516'|' in the *Summary* buffer can be used to pipe the current
 517message to an external program, and this is a handy way to drive
 518"git am".  However, if the message is MIME encoded, what is
 519piped into the program is the representation you see in your
 520*Article* buffer after unwrapping MIME.  This is often not what
 521you would want for two reasons.  It tends to screw up non ASCII
 522characters (most notably in people's names), and also
 523whitespaces (fatal in patches).  Running 'C-u g' to display the
 524message in raw form before using '|' to run the pipe can work
 525this problem around.