Documentation / SubmittingPatcheson commit SubmittingPatches: who am I and who cares? (adcc42e)
   1Checklist (and a short version for the impatient):
   2
   3        Commits:
   4
   5        - make commits of logical units
   6        - check for unnecessary whitespace with "git diff --check"
   7          before committing
   8        - do not check in commented out code or unneeded files
   9        - the first line of the commit message should be a short
  10          description (50 characters is the soft limit, see DISCUSSION
  11          in git-commit(1)), and should skip the full stop
  12        - it is also conventional in most cases to prefix the
  13          first line with "area: " where the area is a filename
  14          or identifier for the general area of the code being
  15          modified, e.g.
  16          . archive: ustar header checksum is computed unsigned
  17          . git-cherry-pick.txt: clarify the use of revision range notation
  18          (if in doubt which identifier to use, run "git log --no-merges"
  19          on the files you are modifying to see the current conventions)
  20        - the body should provide a meaningful commit message, which:
  21          . explains the problem the change tries to solve, iow, what
  22            is wrong with the current code without the change.
  23          . justifies the way the change solves the problem, iow, why
  24            the result with the change is better.
  25          . alternate solutions considered but discarded, if any.
  26        - describe changes in imperative mood, e.g. "make xyzzy do frotz"
  27          instead of "[This patch] makes xyzzy do frotz" or "[I] changed
  28          xyzzy to do frotz", as if you are giving orders to the codebase
  29          to change its behaviour.
  30        - try to make sure your explanation can be understood without
  31          external resources. Instead of giving a URL to a mailing list
  32          archive, summarize the relevant points of the discussion.
  33        - add a "Signed-off-by: Your Name <you@example.com>" line to the
  34          commit message (or just use the option "-s" when committing)
  35          to confirm that you agree to the Developer's Certificate of Origin
  36        - make sure that you have tests for the bug you are fixing
  37        - make sure that the test suite passes after your commit
  38
  39        Patch:
  40
  41        - use "git format-patch -M" to create the patch
  42        - do not PGP sign your patch
  43        - do not attach your patch, but read in the mail
  44          body, unless you cannot teach your mailer to
  45          leave the formatting of the patch alone.
  46        - be careful doing cut & paste into your mailer, not to
  47          corrupt whitespaces.
  48        - provide additional information (which is unsuitable for
  49          the commit message) between the "---" and the diffstat
  50        - if you change, add, or remove a command line option or
  51          make some other user interface change, the associated
  52          documentation should be updated as well.
  53        - if your name is not writable in ASCII, make sure that
  54          you send off a message in the correct encoding.
  55        - send the patch to the list (git@vger.kernel.org) and the
  56          maintainer (gitster@pobox.com) if (and only if) the patch
  57          is ready for inclusion. If you use git-send-email(1),
  58          please test it first by sending email to yourself.
  59        - see below for instructions specific to your mailer
  60
  61Long version:
  62
  63Here are some guidelines for people who want to contribute their code
  64to this software.
  65
  66(0) Decide what to base your work on.
  67
  68In general, always base your work on the oldest branch that your
  69change is relevant to.
  70
  71 - A bugfix should be based on 'maint' in general. If the bug is not
  72   present in 'maint', base it on 'master'. For a bug that's not yet
  73   in 'master', find the topic that introduces the regression, and
  74   base your work on the tip of the topic.
  75
  76 - A new feature should be based on 'master' in general. If the new
  77   feature depends on a topic that is in 'pu', but not in 'master',
  78   base your work on the tip of that topic.
  79
  80 - Corrections and enhancements to a topic not yet in 'master' should
  81   be based on the tip of that topic. If the topic has not been merged
  82   to 'next', it's alright to add a note to squash minor corrections
  83   into the series.
  84
  85 - In the exceptional case that a new feature depends on several topics
  86   not in 'master', start working on 'next' or 'pu' privately and send
  87   out patches for discussion. Before the final merge, you may have to
  88   wait until some of the dependent topics graduate to 'master', and
  89   rebase your work.
  90
  91To find the tip of a topic branch, run "git log --first-parent
  92master..pu" and look for the merge commit. The second parent of this
  93commit is the tip of the topic branch.
  94
  95(1) Make separate commits for logically separate changes.
  96
  97Unless your patch is really trivial, you should not be sending
  98out a patch that was generated between your working tree and
  99your commit head.  Instead, always make a commit with complete
 100commit message and generate a series of patches from your
 101repository.  It is a good discipline.
 102
 103Give an explanation for the change(s) that is detailed enough so
 104that people can judge if it is good thing to do, without reading
 105the actual patch text to determine how well the code does what
 106the explanation promises to do.
 107
 108If your description starts to get too long, that's a sign that you
 109probably need to split up your commit to finer grained pieces.
 110That being said, patches which plainly describe the things that
 111help reviewers check the patch, and future maintainers understand
 112the code, are the most beautiful patches.  Descriptions that summarise
 113the point in the subject well, and describe the motivation for the
 114change, the approach taken by the change, and if relevant how this
 115differs substantially from the prior version, are all good things
 116to have.
 117
 118Oh, another thing.  I am picky about whitespaces.  Make sure your
 119changes do not trigger errors with the sample pre-commit hook shipped
 120in templates/hooks--pre-commit.  To help ensure this does not happen,
 121run git diff --check on your changes before you commit.
 122
 123
 124(2) Generate your patch using git tools out of your commits.
 125
 126git based diff tools generate unidiff which is the preferred format.
 127
 128You do not have to be afraid to use -M option to "git diff" or
 129"git format-patch", if your patch involves file renames.  The
 130receiving end can handle them just fine.
 131
 132Please make sure your patch does not include any extra files
 133which do not belong in a patch submission.  Make sure to review
 134your patch after generating it, to ensure accuracy.  Before
 135sending out, please make sure it cleanly applies to the "master"
 136branch head.  If you are preparing a work based on "next" branch,
 137that is fine, but please mark it as such.
 138
 139
 140(3) Sending your patches.
 141
 142People on the git mailing list need to be able to read and
 143comment on the changes you are submitting.  It is important for
 144a developer to be able to "quote" your changes, using standard
 145e-mail tools, so that they may comment on specific portions of
 146your code.  For this reason, all patches should be submitted
 147"inline".  WARNING: Be wary of your MUAs word-wrap
 148corrupting your patch.  Do not cut-n-paste your patch; you can
 149lose tabs that way if you are not careful.
 150
 151It is a common convention to prefix your subject line with
 152[PATCH].  This lets people easily distinguish patches from other
 153e-mail discussions.  Use of additional markers after PATCH and
 154the closing bracket to mark the nature of the patch is also
 155encouraged.  E.g. [PATCH/RFC] is often used when the patch is
 156not ready to be applied but it is for discussion, [PATCH v2],
 157[PATCH v3] etc. are often seen when you are sending an update to
 158what you have previously sent.
 159
 160"git format-patch" command follows the best current practice to
 161format the body of an e-mail message.  At the beginning of the
 162patch should come your commit message, ending with the
 163Signed-off-by: lines, and a line that consists of three dashes,
 164followed by the diffstat information and the patch itself.  If
 165you are forwarding a patch from somebody else, optionally, at
 166the beginning of the e-mail message just before the commit
 167message starts, you can put a "From: " line to name that person.
 168
 169You often want to add additional explanation about the patch,
 170other than the commit message itself.  Place such "cover letter"
 171material between the three dash lines and the diffstat.
 172
 173Do not attach the patch as a MIME attachment, compressed or not.
 174Do not let your e-mail client send quoted-printable.  Do not let
 175your e-mail client send format=flowed which would destroy
 176whitespaces in your patches. Many
 177popular e-mail applications will not always transmit a MIME
 178attachment as plain text, making it impossible to comment on
 179your code.  A MIME attachment also takes a bit more time to
 180process.  This does not decrease the likelihood of your
 181MIME-attached change being accepted, but it makes it more likely
 182that it will be postponed.
 183
 184Exception:  If your mailer is mangling patches then someone may ask
 185you to re-send them using MIME, that is OK.
 186
 187Do not PGP sign your patch, at least for now.  Most likely, your
 188maintainer or other people on the list would not have your PGP
 189key and would not bother obtaining it anyway.  Your patch is not
 190judged by who you are; a good patch from an unknown origin has a
 191far better chance of being accepted than a patch from a known,
 192respected origin that is done poorly or does incorrect things.
 193
 194If you really really really really want to do a PGP signed
 195patch, format it as "multipart/signed", not a text/plain message
 196that starts with '-----BEGIN PGP SIGNED MESSAGE-----'.  That is
 197not a text/plain, it's something else.
 198
 199Unless your patch is a very trivial and an obviously correct one,
 200first send it with "To:" set to the mailing list, with "cc:" listing
 201people who are involved in the area you are touching (the output from
 202"git blame $path" and "git shortlog --no-merges $path" would help to
 203identify them), to solicit comments and reviews.  After the list
 204reached a consensus that it is a good idea to apply the patch, re-send
 205it with "To:" set to the maintainer and optionally "cc:" the list for
 206inclusion.  Do not forget to add trailers such as "Acked-by:",
 207"Reviewed-by:" and "Tested-by:" after your "Signed-off-by:" line as
 208necessary.
 209
 210
 211(4) Sign your work
 212
 213To improve tracking of who did what, we've borrowed the
 214"sign-off" procedure from the Linux kernel project on patches
 215that are being emailed around.  Although core GIT is a lot
 216smaller project it is a good discipline to follow it.
 217
 218The sign-off is a simple line at the end of the explanation for
 219the patch, which certifies that you wrote it or otherwise have
 220the right to pass it on as a open-source patch.  The rules are
 221pretty simple: if you can certify the below:
 222
 223        Developer's Certificate of Origin 1.1
 224
 225        By making a contribution to this project, I certify that:
 226
 227        (a) The contribution was created in whole or in part by me and I
 228            have the right to submit it under the open source license
 229            indicated in the file; or
 230
 231        (b) The contribution is based upon previous work that, to the best
 232            of my knowledge, is covered under an appropriate open source
 233            license and I have the right under that license to submit that
 234            work with modifications, whether created in whole or in part
 235            by me, under the same open source license (unless I am
 236            permitted to submit under a different license), as indicated
 237            in the file; or
 238
 239        (c) The contribution was provided directly to me by some other
 240            person who certified (a), (b) or (c) and I have not modified
 241            it.
 242
 243        (d) I understand and agree that this project and the contribution
 244            are public and that a record of the contribution (including all
 245            personal information I submit with it, including my sign-off) is
 246            maintained indefinitely and may be redistributed consistent with
 247            this project or the open source license(s) involved.
 248
 249then you just add a line saying
 250
 251        Signed-off-by: Random J Developer <random@developer.example.org>
 252
 253This line can be automatically added by git if you run the git-commit
 254command with the -s option.
 255
 256Notice that you can place your own Signed-off-by: line when
 257forwarding somebody else's patch with the above rules for
 258D-C-O.  Indeed you are encouraged to do so.  Do not forget to
 259place an in-body "From: " line at the beginning to properly attribute
 260the change to its true author (see (2) above).
 261
 262Also notice that a real name is used in the Signed-off-by: line. Please
 263don't hide your real name.
 264
 265If you like, you can put extra tags at the end:
 266
 2671. "Reported-by:" is used to credit someone who found the bug that
 268   the patch attempts to fix.
 2692. "Acked-by:" says that the person who is more familiar with the area
 270   the patch attempts to modify liked the patch.
 2713. "Reviewed-by:", unlike the other tags, can only be offered by the
 272   reviewer and means that she is completely satisfied that the patch
 273   is ready for application.  It is usually offered only after a
 274   detailed review.
 2754. "Tested-by:" is used to indicate that the person applied the patch
 276   and found it to have the desired effect.
 277
 278You can also create your own tag or use one that's in common usage
 279such as "Thanks-to:", "Based-on-patch-by:", or "Mentored-by:".
 280
 281------------------------------------------------
 282An ideal patch flow
 283
 284Here is an ideal patch flow for this project the current maintainer
 285suggests to the contributors:
 286
 287 (0) You come up with an itch.  You code it up.
 288
 289 (1) Send it to the list and cc people who may need to know about
 290     the change.
 291
 292     The people who may need to know are the ones whose code you
 293     are butchering.  These people happen to be the ones who are
 294     most likely to be knowledgeable enough to help you, but
 295     they have no obligation to help you (i.e. you ask for help,
 296     don't demand).  "git log -p -- $area_you_are_modifying" would
 297     help you find out who they are.
 298
 299 (2) You get comments and suggestions for improvements.  You may
 300     even get them in a "on top of your change" patch form.
 301
 302 (3) Polish, refine, and re-send to the list and the people who
 303     spend their time to improve your patch.  Go back to step (2).
 304
 305 (4) The list forms consensus that the last round of your patch is
 306     good.  Send it to the list and cc the maintainer.
 307
 308 (5) A topic branch is created with the patch and is merged to 'next',
 309     and cooked further and eventually graduates to 'master'.
 310
 311In any time between the (2)-(3) cycle, the maintainer may pick it up
 312from the list and queue it to 'pu', in order to make it easier for
 313people play with it without having to pick up and apply the patch to
 314their trees themselves.
 315
 316------------------------------------------------
 317Know the status of your patch after submission
 318
 319* You can use Git itself to find out when your patch is merged in
 320  master. 'git pull --rebase' will automatically skip already-applied
 321  patches, and will let you know. This works only if you rebase on top
 322  of the branch in which your patch has been merged (i.e. it will not
 323  tell you if your patch is merged in pu if you rebase on top of
 324  master).
 325
 326* Read the git mailing list, the maintainer regularly posts messages
 327  entitled "What's cooking in git.git" and "What's in git.git" giving
 328  the status of various proposed changes.
 329
 330------------------------------------------------
 331MUA specific hints
 332
 333Some of patches I receive or pick up from the list share common
 334patterns of breakage.  Please make sure your MUA is set up
 335properly not to corrupt whitespaces.
 336
 337See the DISCUSSION section of git-format-patch(1) for hints on
 338checking your patch by mailing it to yourself and applying with
 339git-am(1).
 340
 341While you are at it, check the resulting commit log message from
 342a trial run of applying the patch.  If what is in the resulting
 343commit is not exactly what you would want to see, it is very
 344likely that your maintainer would end up hand editing the log
 345message when he applies your patch.  Things like "Hi, this is my
 346first patch.\n", if you really want to put in the patch e-mail,
 347should come after the three-dash line that signals the end of the
 348commit message.
 349
 350
 351Pine
 352----
 353
 354(Johannes Schindelin)
 355
 356I don't know how many people still use pine, but for those poor
 357souls it may be good to mention that the quell-flowed-text is
 358needed for recent versions.
 359
 360... the "no-strip-whitespace-before-send" option, too. AFAIK it
 361was introduced in 4.60.
 362
 363(Linus Torvalds)
 364
 365And 4.58 needs at least this.
 366
 367---
 368diff-tree 8326dd8350be64ac7fc805f6563a1d61ad10d32c (from e886a61f76edf5410573e92e38ce22974f9c40f1)
 369Author: Linus Torvalds <torvalds@g5.osdl.org>
 370Date:   Mon Aug 15 17:23:51 2005 -0700
 371
 372    Fix pine whitespace-corruption bug
 373
 374    There's no excuse for unconditionally removing whitespace from
 375    the pico buffers on close.
 376
 377diff --git a/pico/pico.c b/pico/pico.c
 378--- a/pico/pico.c
 379+++ b/pico/pico.c
 380@@ -219,7 +219,9 @@ PICO *pm;
 381            switch(pico_all_done){      /* prepare for/handle final events */
 382              case COMP_EXIT :          /* already confirmed */
 383                packheader();
 384+#if 0
 385                stripwhitespace();
 386+#endif
 387                c |= COMP_EXIT;
 388                break;
 389
 390
 391(Daniel Barkalow)
 392
 393> A patch to SubmittingPatches, MUA specific help section for
 394> users of Pine 4.63 would be very much appreciated.
 395
 396Ah, it looks like a recent version changed the default behavior to do the
 397right thing, and inverted the sense of the configuration option. (Either
 398that or Gentoo did it.) So you need to set the
 399"no-strip-whitespace-before-send" option, unless the option you have is
 400"strip-whitespace-before-send", in which case you should avoid checking
 401it.
 402
 403
 404Thunderbird, KMail, GMail
 405-------------------------
 406
 407See the MUA-SPECIFIC HINTS section of git-format-patch(1).
 408
 409Gnus
 410----
 411
 412'|' in the *Summary* buffer can be used to pipe the current
 413message to an external program, and this is a handy way to drive
 414"git am".  However, if the message is MIME encoded, what is
 415piped into the program is the representation you see in your
 416*Article* buffer after unwrapping MIME.  This is often not what
 417you would want for two reasons.  It tends to screw up non ASCII
 418characters (most notably in people's names), and also
 419whitespaces (fatal in patches).  Running 'C-u g' to display the
 420message in raw form before using '|' to run the pipe can work
 421this problem around.