doc/SubmittingPatches: improve text formatting
[git/git.git] / Documentation / SubmittingPatches
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049e64aa 1Submitting Patches
2==================
3
4== Guidelines
5
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6Here are some guidelines for people who want to contribute their code
7to this software.
31408251 8
049e64aa 9[[base-branch]]
10=== Decide what to base your work on.
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11
12In general, always base your work on the oldest branch that your
13change is relevant to.
14
049e64aa 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.
d0c26f0f 19
049e64aa 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.
d0c26f0f 23
049e64aa 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.
d0c26f0f 28
049e64aa 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.
d0c26f0f 34
049e64aa 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.
e6da8ee8 38
049e64aa 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
d0c26f0f 41commit is the tip of the topic branch.
31408251 42
049e64aa 43[[separate-commits]]
44=== Make separate commits for logically separate changes.
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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
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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.
31408251 56
45d2b286 57If your description starts to get too long, that's a sign that you
31408251 58probably need to split up your commit to finer grained pieces.
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59That being said, patches which plainly describe the things that
60help reviewers check the patch, and future maintainers understand
01e60a9a 61the code, are the most beautiful patches. Descriptions that summarize
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62the point in the subject well, and describe the motivation for the
63change, the approach taken by the change, and if relevant how this
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64differs substantially from the prior version, are all good things
65to have.
31408251 66
54cc5d29 67Make sure that you have tests for the bug you are fixing. See
049e64aa 68`t/README` for guidance.
7d5bf87b 69
049e64aa 70[[tests]]
7d5bf87b 71When adding a new feature, make sure that you have new tests to show
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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.
42e0fae9 94
049e64aa 95[[whitespace-check]]
42e0fae9 96Oh, another thing. We are picky about whitespaces. Make sure your
45d2b286 97changes do not trigger errors with the sample pre-commit hook shipped
049e64aa 98in `templates/hooks--pre-commit`. To help ensure this does not happen,
99run `git diff --check` on your changes before you commit.
31408251 100
049e64aa 101[[describe-changes]]
102=== Describe your changes well.
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103
104The first line of the commit message should be a short description (50
049e64aa 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
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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
049e64aa 110* doc: clarify distinction between sign-off and pgp-signing
111* githooks.txt: improve the intro section
7d5bf87b 112
049e64aa 113If in doubt which identifier to use, run `git log --no-merges` on the
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114files you are modifying to see the current conventions.
115
049e64aa 116[[summary-section]]
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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
049e64aa 122[[meaningful-message]]
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123The body should provide a meaningful commit message, which:
124
049e64aa 125. explains the problem the change tries to solve, i.e. what is wrong
126 with the current code without the change.
7d5bf87b 127
049e64aa 128. justifies the way the change solves the problem, i.e. why the
129 result with the change is better.
7d5bf87b 130
049e64aa 131. alternate solutions considered but discarded, if any.
7d5bf87b 132
049e64aa 133[[imperative-mood]]
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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
01e60a9a 137its behavior. Try to make sure your explanation can be understood
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138without external resources. Instead of giving a URL to a mailing list
139archive, summarize the relevant points of the discussion.
140
049e64aa 141[[commit-reference]]
175d38ca 142If you want to reference a previous commit in the history of a stable
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143branch, use the format "abbreviated sha1 (subject, date)",
144with the subject enclosed in a pair of double-quotes, like this:
145
049e64aa 146....
147 Commit f86a374 ("pack-bitmap.c: fix a memleak", 2015-03-30)
148 noticed that ...
149....
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150
151The "Copy commit summary" command of gitk can be used to obtain this
049e64aa 152format, or this invocation of `git show`:
175d38ca 153
049e64aa 154....
155 git show -s --date=short --pretty='format:%h ("%s", %ad)' <commit>
156....
7d5bf87b 157
049e64aa 158[[git-tools]]
159=== Generate your patch using Git tools out of your commits.
45d2b286 160
2de9b711 161Git based diff tools generate unidiff which is the preferred format.
45d2b286 162
049e64aa 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
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165receiving end can handle them just fine.
166
049e64aa 167[[review-patch]]
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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
31408251 171your patch after generating it, to ensure accuracy. Before
049e64aa 172sending out, please make sure it cleanly applies to the `master`
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173branch head. If you are preparing a work based on "next" branch,
174that is fine, but please mark it as such.
31408251 175
049e64aa 176[[send-patches]]
177=== Sending your patches.
31408251 178
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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
2de9b711 184People on the Git mailing list need to be able to read and
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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
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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
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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
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201corrupting your patch. Do not cut-n-paste your patch; you can
202lose tabs that way if you are not careful.
31408251 203
45d2b286 204It is a common convention to prefix your subject line with
31408251 205[PATCH]. This lets people easily distinguish patches from other
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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.
31408251 212
049e64aa 213`git format-patch` command follows the best current practice to
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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"
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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`.
31408251 229
049e64aa 230[[attachment]]
31408251 231Do not attach the patch as a MIME attachment, compressed or not.
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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
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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
9847f7e0 243you to re-send them using MIME, that is OK.
31408251 244
049e64aa 245[[pgp-signature]]
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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.
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251
252If you really really really really want to do a PGP signed
253patch, format it as "multipart/signed", not a text/plain message
049e64aa 254that starts with `-----BEGIN PGP SIGNED MESSAGE-----`. That is
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255not a text/plain, it's something else.
256
7d5bf87b 257Send your patch with "To:" set to the mailing list, with "cc:" listing
d0c26f0f 258people who are involved in the area you are touching (the output from
c9e3d472 259`git blame $path` and `git shortlog --no-merges $path` would help to
7d5bf87b 260identify them), to solicit comments and reviews.
04d24455 261
049e64aa 262:1: footnote:[The current maintainer: gitster@pobox.com]
263:2: footnote:[The mailing list: git@vger.kernel.org]
264
7d5bf87b 265After the list reached a consensus that it is a good idea to apply the
049e64aa 266patch, re-send it with "To:" set to the maintainer{1} and "cc:" the
267list{2} for inclusion.
31408251 268
049e64aa 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
7d5bf87b 271patch.
04d24455 272
049e64aa 273[[sign-off]]
274=== Certify your work by adding your "Signed-off-by: " line
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275
276To improve tracking of who did what, we've borrowed the
277"sign-off" procedure from the Linux kernel project on patches
48a8c26c 278that are being emailed around. Although core Git is a lot
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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
01e60a9a 284pretty simple: if you can certify the below D-C-O:
31408251 285
049e64aa 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____
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313
314then you just add a line saying
315
049e64aa 316....
317 Signed-off-by: Random J Developer <random@developer.example.org>
318....
31408251 319
2de9b711 320This line can be automatically added by Git if you run the git-commit
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321command with the -s option.
322
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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
049e64aa 329[[real-name]]
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330Also notice that a real name is used in the Signed-off-by: line. Please
331don't hide your real name.
332
049e64aa 333[[commit-trailers]]
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334If you like, you can put extra tags at the end:
335
049e64aa 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.
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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:".
9740d289 349
049e64aa 350== Subsystems with dedicated maintainers
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351
352Some parts of the system have dedicated maintainers with their own
353repositories.
354
049e64aa 355- 'git-gui/' comes from git-gui project, maintained by Pat Thoyts:
e6da8ee8 356
049e64aa 357 git://repo.or.cz/git-gui.git
e6da8ee8 358
049e64aa 359- 'gitk-git/' comes from Paul Mackerras's gitk project:
e6da8ee8 360
049e64aa 361 git://ozlabs.org/~paulus/gitk
e6da8ee8 362
049e64aa 363- 'po/' comes from the localization coordinator, Jiang Xin:
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364
365 https://github.com/git-l10n/git-po/
366
367Patches to these parts should be based on their trees.
368
049e64aa 369[[patch-flow]]
370== An ideal patch flow
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371
372Here is an ideal patch flow for this project the current maintainer
373suggests to the contributors:
374
049e64aa 375. You come up with an itch. You code it up.
a941fb4a 376
049e64aa 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.
a941fb4a 386
049e64aa 387. You get comments and suggestions for improvements. You may
388 even get them in a "on top of your change" patch form.
a941fb4a 389
049e64aa 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).
a941fb4a 392
049e64aa 393. The list forms consensus that the last round of your patch is
394 good. Send it to the maintainer and cc the list.
a941fb4a 395
049e64aa 396. A topic branch is created with the patch and is merged to `next`,
397 and cooked further and eventually graduates to `master`.
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398
399In any time between the (2)-(3) cycle, the maintainer may pick it up
049e64aa 400from the list and queue it to `pu`, in order to make it easier for
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401people play with it without having to pick up and apply the patch to
402their trees themselves.
403
049e64aa 404[[patch-status]]
405== Know the status of your patch after submission
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406
407* You can use Git itself to find out when your patch is merged in
049e64aa 408 master. `git pull --rebase` will automatically skip already-applied
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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
2de9b711 414* Read the Git mailing list, the maintainer regularly posts messages
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415 entitled "What's cooking in git.git" and "What's in git.git" giving
416 the status of various proposed changes.
417
049e64aa 418[[travis]]
419== GitHub-Travis CI hints
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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
049e64aa 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/
0e5d028a 431
049e64aa 432. Open the Travis CI website: https://travis-ci.org
0e5d028a 433
049e64aa 434. Press the "Sign in with GitHub" button.
0e5d028a 435
049e64aa 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
0e5d028a 439
049e64aa 440. Open your Travis CI profile page: https://travis-ci.org/profile
0e5d028a 441
049e64aa 442. Enable Travis CI builds for your Git fork.
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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
049e64aa 446branches here: https://travis-ci.org/__<Your GitHub handle>__/git/branches
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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
049e64aa 458[[mua]]
459== MUA specific hints
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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
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463properly not to corrupt whitespaces.
464
049e64aa 465See the DISCUSSION section of linkgit:git-format-patch[1] for hints on
57756161 466checking your patch by mailing it to yourself and applying with
049e64aa 467linkgit:git-am[1].
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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.
9847f7e0 477
9740d289 478
049e64aa 479=== Pine
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480
481(Johannes Schindelin)
482
049e64aa 483....
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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.
049e64aa 490....
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491
492(Linus Torvalds)
493
049e64aa 494....
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495And 4.58 needs at least this.
496
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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;
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510 switch(pico_all_done){ /* prepare for/handle final events */
511 case COMP_EXIT : /* already confirmed */
512 packheader();
9740d289 513+#if 0
a6080a0a 514 stripwhitespace();
9740d289 515+#endif
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516 c |= COMP_EXIT;
517 break;
049e64aa 518....
9740d289 519
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520(Daniel Barkalow)
521
049e64aa 522....
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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.
049e64aa 532....
1eb446fa 533
049e64aa 534=== Thunderbird, KMail, GMail
9740d289 535
049e64aa 536See the MUA-SPECIFIC HINTS section of linkgit:git-format-patch[1].
e30b217b 537
049e64aa 538=== Gnus
e30b217b 539
049e64aa 540"|" in the `*Summary*` buffer can be used to pipe the current
e30b217b 541message to an external program, and this is a handy way to drive
049e64aa 542`git am`. However, if the message is MIME encoded, what is
e30b217b 543piped into the program is the representation you see in your
049e64aa 544`*Article*` buffer after unwrapping MIME. This is often not what
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JH
545you would want for two reasons. It tends to screw up non ASCII
546characters (most notably in people's names), and also
049e64aa 547whitespaces (fatal in patches). Running "C-u g" to display the
548message in raw form before using "|" to run the pipe can work
e30b217b 549this problem around.