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1=encoding utf8
2
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3=for comment
4Consistent formatting of this file is achieved with:
04c692a8 5 perl ./Porting/podtidy pod/perlgit.pod
0549aefb 6
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7=head1 NAME
8
04c692a8 9perlgit - Detailed information about git and the Perl repository
d7dd28b6 10
04c692a8 11=head1 DESCRIPTION
d7dd28b6 12
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13This document provides details on using git to develop Perl. If you are
14just interested in working on a quick patch, see L<perlhack> first.
15This document is intended for people who are regular contributors to
16Perl, including those with write access to the git repository.
184487f0 17
04c692a8 18=head1 CLONING THE REPOSITORY
f6c12373 19
04c692a8 20All of Perl's source code is kept centrally in a Git repository at
47ef154c 21I<github.com>.
f6c12373 22
04c692a8 23You can make a read-only clone of the repository by running:
f6c12373 24
47ef154c 25 % git clone git://github.com/Perl/perl5.git perl
f6c12373 26
04c692a8 27This uses the git protocol (port 9418).
f6c12373 28
04c692a8 29If you cannot use the git protocol for firewall reasons, you can also
47ef154c 30clone via http:
3482f01a 31
47ef154c 32 % git clone https://github.com/Perl/perl5.git perl
b47aa495 33
04c692a8 34=head1 WORKING WITH THE REPOSITORY
d7dd28b6 35
6acba58e 36Once you have changed into the repository directory, you can inspect
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37it. After a clone the repository will contain a single local branch,
38which will be the current branch as well, as indicated by the asterisk.
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39
40 % git branch
41 * blead
42
f755e97d 43Using the -a switch to C<branch> will also show the remote tracking
6acba58e 44branches in the repository:
39219fd3 45
d9847473 46 % git branch -a
09081495 47 * blead
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48 origin/HEAD
49 origin/blead
50 ...
51
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52The branches that begin with "origin" correspond to the "git remote"
53that you cloned from (which is named "origin"). Each branch on the
c9d1da35 54remote will be exactly tracked by these branches. You should NEVER do
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55work on these remote tracking branches. You only ever do work in a
56local branch. Local branches can be configured to automerge (on pull)
57from a designated remote tracking branch. This is the case with the
58default branch C<blead> which will be configured to merge from the
59remote tracking branch C<origin/blead>.
39219fd3 60
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61You can see recent commits:
62
c2cf2042 63 % git log
d7dd28b6 64
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65And pull new changes from the repository, and update your local
66repository (must be clean first)
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67
68 % git pull
09081495 69
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70Assuming we are on the branch C<blead> immediately after a pull, this
71command would be more or less equivalent to:
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72
73 % git fetch
74 % git merge origin/blead
75
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76In fact if you want to update your local repository without touching
77your working directory you do:
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78
79 % git fetch
80
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81And if you want to update your remote-tracking branches for all defined
82remotes simultaneously you can do
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83
84 % git remote update
85
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86Neither of these last two commands will update your working directory,
87however both will update the remote-tracking branches in your
88repository.
39219fd3 89
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90To make a local branch of a remote branch:
91
92 % git checkout -b maint-5.10 origin/maint-5.10
93
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94To switch back to blead:
95
96 % git checkout blead
c2cf2042 97
ba336be1 98=head2 Finding out your status
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99
100The most common git command you will use will probably be
101
102 % git status
103
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104This command will produce as output a description of the current state
105of the repository, including modified files and unignored untracked
106files, and in addition it will show things like what files have been
107staged for the next commit, and usually some useful information about
108how to change things. For instance the following:
39219fd3 109
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110 % git status
111 On branch blead
112 Your branch is ahead of 'origin/blead' by 1 commit.
82217626 113
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114 Changes to be committed:
115 (use "git reset HEAD <file>..." to unstage)
82217626 116
c7956846 117 modified: pod/perlgit.pod
82217626 118
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119 Changes not staged for commit:
120 (use "git add <file>..." to update what will be committed)
121 (use "git checkout -- <file>..." to discard changes in working
122 directory)
82217626 123
c7956846 124 modified: pod/perlgit.pod
82217626 125
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126 Untracked files:
127 (use "git add <file>..." to include in what will be committed)
82217626 128
c7956846 129 deliberate.untracked
39219fd3 130
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131This shows that there were changes to this document staged for commit,
132and that there were further changes in the working directory not yet
133staged. It also shows that there was an untracked file in the working
134directory, and as you can see shows how to change all of this. It also
0549aefb 135shows that there is one commit on the working branch C<blead> which has
ff28a605 136not been pushed to the C<origin> remote yet. B<NOTE>: This output
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137is also what you see as a template if you do not provide a message to
138C<git commit>.
7f6effc7 139
04c692a8 140=head2 Patch workflow
7f6effc7 141
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142First, please read L<perlhack> for details on hacking the Perl core.
143That document covers many details on how to create a good patch.
7f6effc7 144
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145If you already have a Perl repository, you should ensure that you're on
146the I<blead> branch, and your repository is up to date:
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147
148 % git checkout blead
149 % git pull
150
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151It's preferable to patch against the latest blead version, since this
152is where new development occurs for all changes other than critical bug
04c692a8 153fixes. Critical bug fix patches should be made against the relevant
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154maint branches, or should be submitted with a note indicating all the
155branches where the fix should be applied.
a44f43ac 156
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157Now that we have everything up to date, we need to create a temporary
158new branch for these changes and switch into it:
b1fccde5 159
a9b05323 160 % git checkout -b orange
23f8d33e 161
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162which is the short form of
163
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164 % git branch orange
165 % git checkout orange
166
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167Creating a topic branch makes it easier for the maintainers to rebase
168or merge back into the master blead for a more linear history. If you
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169don't work on a topic branch the maintainer has to manually cherry pick
170your changes onto blead before they can be applied.
0c24b290 171
77db6475 172That'll get you scolded on perl5-porters, so don't do that. Be Awesome.
0c24b290 173
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174Then make your changes. For example, if Leon Brocard changes his name
175to Orange Brocard, we should change his name in the AUTHORS file:
176
177 % perl -pi -e 's{Leon Brocard}{Orange Brocard}' AUTHORS
178
179You can see what files are changed:
180
181 % git status
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182 On branch orange
183 Changes to be committed:
184 (use "git reset HEAD <file>..." to unstage)
185
186 modified: AUTHORS
c2cf2042 187
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188And you can see the changes:
189
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190 % git diff
191 diff --git a/AUTHORS b/AUTHORS
192 index 293dd70..722c93e 100644
193 --- a/AUTHORS
194 +++ b/AUTHORS
195 @@ -541,7 +541,7 @@ Lars Hecking <lhecking@nmrc.ucc.ie>
196 Laszlo Molnar <laszlo.molnar@eth.ericsson.se>
197 Leif Huhn <leif@hale.dkstat.com>
198 Len Johnson <lenjay@ibm.net>
199 -Leon Brocard <acme@astray.com>
200 +Orange Brocard <acme@astray.com>
201 Les Peters <lpeters@aol.net>
202 Lesley Binks <lesley.binks@gmail.com>
203 Lincoln D. Stein <lstein@cshl.org>
c2cf2042 204
04c692a8 205Now commit your change locally:
77471e41 206
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207 % git commit -a -m 'Rename Leon Brocard to Orange Brocard'
208 Created commit 6196c1d: Rename Leon Brocard to Orange Brocard
209 1 files changed, 1 insertions(+), 1 deletions(-)
77471e41 210
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211The C<-a> option is used to include all files that git tracks that you
212have changed. If at this time, you only want to commit some of the
213files you have worked on, you can omit the C<-a> and use the command
214C<S<git add I<FILE ...>>> before doing the commit. C<S<git add
215--interactive>> allows you to even just commit portions of files
216instead of all the changes in them.
77471e41 217
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218The C<-m> option is used to specify the commit message. If you omit it,
219git will open a text editor for you to compose the message
220interactively. This is useful when the changes are more complex than
221the sample given here, and, depending on the editor, to know that the
222first line of the commit message doesn't exceed the 50 character legal
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223maximum. See L<perlhack/Commit message> for more information about what
224makes a good commit message.
77471e41 225
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226Once you've finished writing your commit message and exited your
227editor, git will write your change to disk and tell you something like
228this:
77471e41 229
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230 Created commit daf8e63: explain git status and stuff about remotes
231 1 files changed, 83 insertions(+), 3 deletions(-)
c2cf2042 232
04c692a8 233If you re-run C<git status>, you should see something like this:
c2cf2042 234
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235 % git status
236 On branch orange
237 Untracked files:
238 (use "git add <file>..." to include in what will be committed)
82217626 239
c7956846 240 deliberate.untracked
82217626 241
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242 nothing added to commit but untracked files present (use "git add" to
243 track)
2be70973 244
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245When in doubt, before you do anything else, check your status and read
246it carefully, many questions are answered directly by the git status
247output.
2be70973 248
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249You can examine your last commit with:
250
251 % git show HEAD
252
253and if you are not happy with either the description or the patch
c26da522 254itself you can fix it up by editing the files once more and then issue:
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255
256 % git commit -a --amend
257
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258Now, create a fork on GitHub to push your branch to, and add it as a
259remote if you haven't already, as described in the GitHub documentation
260at L<https://help.github.com/en/articles/working-with-forks>:
c2cf2042 261
617d9ec4 262 % git remote add fork git@github.com:MyUser/perl5.git
c2cf2042 263
617d9ec4 264And push the branch to your fork:
9420b3b3 265
617d9ec4 266 % git push -u fork orange
9420b3b3 267
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268You should now submit a Pull Request (PR) on GitHub from the new branch
269to blead. For more information, see the GitHub documentation at
270L<https://help.github.com/en/articles/creating-a-pull-request-from-a-fork>.
271
272You can also send patch files to
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273L<perl5-porters@perl.org|mailto:perl5-porters@perl.org> directly if the
274patch is not ready to be applied, but intended for discussion.
64a8e22b 275
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276To create a patch file for all your local changes:
277
278 % git format-patch -M blead..
279 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
280
281Or for a lot of changes, e.g. from a topic branch:
282
283 % git format-patch --stdout -M blead.. > topic-branch-changes.patch
c2cf2042 284
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285If you want to delete your temporary branch, you may do so with:
286
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287 % git checkout blead
288 % git branch -d orange
289 error: The branch 'orange' is not an ancestor of your current HEAD.
290 If you are sure you want to delete it, run 'git branch -D orange'.
291 % git branch -D orange
292 Deleted branch orange.
7df2e4bc 293
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294=head2 A note on derived files
295
296Be aware that many files in the distribution are derivative--avoid
0549aefb 297patching them, because git won't see the changes to them, and the build
04c692a8 298process will overwrite them. Patch the originals instead. Most
0549aefb 299utilities (like perldoc) are in this category, i.e. patch
77db6475 300F<utils/perldoc.PL> rather than F<utils/perldoc>. Similarly, don't
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301create patches for files under F<$src_root/ext> from their copies found
302in F<$install_root/lib>. If you are unsure about the proper location of
303a file that may have gotten copied while building the source
304distribution, consult the F<MANIFEST>.
a44f43ac 305
04c692a8 306=head2 Cleaning a working directory
b0d36535 307
6acba58e 308The command C<git clean> can with varying arguments be used as a
dc3c3040 309replacement for C<make clean>.
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310
311To reset your working directory to a pristine condition you can do:
312
e0b2b458 313 % git clean -dxf
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314
315However, be aware this will delete ALL untracked content. You can use
316
e0b2b458 317 % git clean -Xf
b0d36535 318
6acba58e 319to remove all ignored untracked files, such as build and test
11fa7e22 320byproduct, but leave any manually created files alone.
b0d36535 321
0549aefb 322If you only want to cancel some uncommitted edits, you can use C<git
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323checkout> and give it a list of files to be reverted, or C<git checkout
324-f> to revert them all.
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325
326If you want to cancel one or several commits, you can use C<git reset>.
327
04c692a8 328=head2 Bisecting
d82a90c1 329
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330C<git> provides a built-in way to determine which commit should be blamed
331for introducing a given bug. C<git bisect> performs a binary search of
332history to locate the first failing commit. It is fast, powerful and
333flexible, but requires some setup and to automate the process an auxiliary
334shell script is needed.
335
336The core provides a wrapper program, F<Porting/bisect.pl>, which attempts to
337simplify as much as possible, making bisecting as simple as running a Perl
338one-liner. For example, if you want to know when this became an error:
339
340 perl -e 'my $a := 2'
341
342you simply run this:
343
344 .../Porting/bisect.pl -e 'my $a := 2;'
345
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346Using F<Porting/bisect.pl>, with one command (and no other files) it's easy to
347find out
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348
349=over 4
350
351=item *
352
353Which commit caused this example code to break?
354
355=item *
356
357Which commit caused this example code to start working?
358
359=item *
360
361Which commit added the first file to match this regex?
362
363=item *
364
365Which commit removed the last file to match this regex?
366
367=back
368
369usually without needing to know which versions of perl to use as start and
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370end revisions, as F<Porting/bisect.pl> automatically searches to find the
371earliest stable version for which the test case passes. Run
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372C<Porting/bisect.pl --help> for the full documentation, including how to
373set the C<Configure> and build time options.
374
375If you require more flexibility than F<Porting/bisect.pl> has to offer, you'll
376need to run C<git bisect> yourself. It's most useful to use C<git bisect run>
377to automate the building and testing of perl revisions. For this you'll need
378a shell script for C<git> to call to test a particular revision. An example
379script is F<Porting/bisect-example.sh>, which you should copy B<outside> of
380the repository, as the bisect process will reset the state to a clean checkout
381as it runs. The instructions below assume that you copied it as F<~/run> and
382then edited it as appropriate.
d82a90c1 383
bdaf0bc6 384You first enter in bisect mode with:
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385
386 % git bisect start
387
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388For example, if the bug is present on C<HEAD> but wasn't in 5.10.0,
389C<git> will learn about this when you enter:
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390
391 % git bisect bad
392 % git bisect good perl-5.10.0
393 Bisecting: 853 revisions left to test after this
394
6acba58e 395This results in checking out the median commit between C<HEAD> and
bdaf0bc6 396C<perl-5.10.0>. You can then run the bisecting process with:
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397
398 % git bisect run ~/run
399
400When the first bad commit is isolated, C<git bisect> will tell you so:
401
402 ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5 is first bad commit
403 commit ca4cfd28534303b82a216cfe83a1c80cbc3b9dc5
404 Author: Dave Mitchell <davem@fdisolutions.com>
405 Date: Sat Feb 9 14:56:23 2008 +0000
406
9469eb4a 407 [perl #49472] Attributes + Unknown Error
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408 ...
409
410 bisect run success
411
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412You can peek into the bisecting process with C<git bisect log> and
413C<git bisect visualize>. C<git bisect reset> will get you out of bisect
414mode.
d82a90c1 415
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416Please note that the first C<good> state must be an ancestor of the
417first C<bad> state. If you want to search for the commit that I<solved>
418some bug, you have to negate your test case (i.e. exit with C<1> if OK
419and C<0> if not) and still mark the lower bound as C<good> and the
420upper as C<bad>. The "first bad commit" has then to be understood as
421the "first commit where the bug is solved".
d82a90c1 422
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423C<git help bisect> has much more information on how you can tweak your
424binary searches.
feb5e972 425
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426Following bisection you may wish to configure, build and test perl at
427commits identified by the bisection process. Sometimes, particularly
428with older perls, C<make> may fail during this process. In this case
429you may be able to patch the source code at the older commit point. To
430do so, please follow the suggestions provided in
431L<perlhack/Building perl at older commits>.
432
99cd8e46 433=head2 Topic branches and rewriting history
9d68b7ed 434
04c692a8 435Individual committers should create topic branches under
04edae75 436B<yourname>/B<some_descriptive_name>:
03050721 437
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438 % branch="$yourname/$some_descriptive_name"
439 % git checkout -b $branch
04edae75 440 ... do local edits, commits etc ...
ff28a605 441 % git push origin -u $branch
03050721 442
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443Should you be stuck with an ancient version of git (prior to 1.7), then
444C<git push> will not have the C<-u> switch, and you have to replace the
445last step with the following sequence:
446
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447 % git push origin $branch:refs/heads/$branch
448 % git config branch.$branch.remote origin
449 % git config branch.$branch.merge refs/heads/$branch
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450
451If you want to make changes to someone else's topic branch, you should
452check with its creator before making any change to it.
453
454You
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455might sometimes find that the original author has edited the branch's
456history. There are lots of good reasons for this. Sometimes, an author
457might simply be rebasing the branch onto a newer source point.
458Sometimes, an author might have found an error in an early commit which
459they wanted to fix before merging the branch to blead.
c26da522 460
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461Currently the master repository is configured to forbid
462non-fast-forward merges. This means that the branches within can not be
463rebased and pushed as a single step.
c26da522 464
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465The only way you will ever be allowed to rebase or modify the history
466of a pushed branch is to delete it and push it as a new branch under
467the same name. Please think carefully about doing this. It may be
468better to sequentially rename your branches so that it is easier for
469others working with you to cherry-pick their local changes onto the new
470version. (XXX: needs explanation).
c26da522 471
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472If you want to rebase a personal topic branch, you will have to delete
473your existing topic branch and push as a new version of it. You can do
474this via the following formula (see the explanation about C<refspec>'s
475in the git push documentation for details) after you have rebased your
476branch:
c26da522 477
cc116ce7 478 # first rebase
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479 % git checkout $user/$topic
480 % git fetch
481 % git rebase origin/blead
c26da522 482
cc116ce7 483 # then "delete-and-push"
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484 % git push origin :$user/$topic
485 % git push origin $user/$topic
c26da522 486
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487B<NOTE:> it is forbidden at the repository level to delete any of the
488"primary" branches. That is any branch matching
489C<m!^(blead|maint|perl)!>. Any attempt to do so will result in git
490producing an error like this:
c26da522 491
ff28a605 492 % git push origin :blead
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493 *** It is forbidden to delete blead/maint branches in this repository
494 error: hooks/update exited with error code 1
495 error: hook declined to update refs/heads/blead
496 To ssh://perl5.git.perl.org/perl
497 ! [remote rejected] blead (hook declined)
498 error: failed to push some refs to 'ssh://perl5.git.perl.org/perl'
c26da522 499
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500As a matter of policy we do B<not> edit the history of the blead and
501maint-* branches. If a typo (or worse) sneaks into a commit to blead or
502maint-*, we'll fix it in another commit. The only types of updates
e7f1d4a7 503allowed on these branches are "fast-forwards", where all history is
04c692a8 504preserved.
2bab0636 505
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506Annotated tags in the canonical perl.git repository will never be
507deleted or modified. Think long and hard about whether you want to push
e7f1d4a7 508a local tag to perl.git before doing so. (Pushing simple tags is
04c692a8 509not allowed.)
2bab0636 510
feb5e972 511=head2 Grafts
c26da522 512
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513The perl history contains one mistake which was not caught in the
514conversion: a merge was recorded in the history between blead and
515maint-5.10 where no merge actually occurred. Due to the nature of git,
516this is now impossible to fix in the public repository. You can remove
517this mis-merge locally by adding the following line to your
518C<.git/info/grafts> file:
c26da522 519
c7956846 520 296f12bbbbaa06de9be9d09d3dcf8f4528898a49 434946e0cb7a32589ed92d18008aaa1d88515930
c26da522 521
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522It is particularly important to have this graft line if any bisecting
523is done in the area of the "merge" in question.
ce2a8773 524
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525=head1 WRITE ACCESS TO THE GIT REPOSITORY
526
527Once you have write access, you will need to modify the URL for the
528origin remote to enable pushing. Edit F<.git/config> with the
529git-config(1) command:
530
47ef154c 531 % git config remote.origin.url git@github.com:Perl/perl5.git
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532
533You can also set up your user name and e-mail address. Most people do
534this once globally in their F<~/.gitconfig> by doing something like:
535
536 % git config --global user.name "Ævar Arnfjörð Bjarmason"
537 % git config --global user.email avarab@gmail.com
538
ff28a605 539However, if you'd like to override that just for perl,
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540execute something like the following in F<perl>:
541
542 % git config user.email avar@cpan.org
543
544It is also possible to keep C<origin> as a git remote, and add a new
545remote for ssh access:
546
47ef154c 547 % git remote add camel git@github.com:Perl/perl5.git
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548
549This allows you to update your local repository by pulling from
550C<origin>, which is faster and doesn't require you to authenticate, and
551to push your changes back with the C<camel> remote:
552
553 % git fetch camel
554 % git push camel
555
556The C<fetch> command just updates the C<camel> refs, as the objects
557themselves should have been fetched when pulling from C<origin>.
04baf1ff 558
99cd8e46 559=head2 Accepting a patch
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560
561If you have received a patch file generated using the above section,
562you should try out the patch.
563
564First we need to create a temporary new branch for these changes and
565switch into it:
566
c7956846 567 % git checkout -b experimental
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568
569Patches that were formatted by C<git format-patch> are applied with
570C<git am>:
571
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572 % git am 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
573 Applying Rename Leon Brocard to Orange Brocard
04c692a8 574
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575Note that some UNIX mail systems can mess with text attachments containing
576'From '. This will fix them up:
577
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578 % perl -pi -e's/^>From /From /' \
579 0001-Rename-Leon-Brocard-to-Orange-Brocard.patch
6fc2106e 580
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581If just a raw diff is provided, it is also possible use this two-step
582process:
583
11fa7e22 584 % git apply bugfix.diff
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585 % git commit -a -m "Some fixing" \
586 --author="That Guy <that.guy@internets.com>"
edcf105d 587
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588Now we can inspect the change:
589
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590 % git show HEAD
591 commit b1b3dab48344cff6de4087efca3dbd63548ab5e2
592 Author: Leon Brocard <acme@astray.com>
593 Date: Fri Dec 19 17:02:59 2008 +0000
594
595 Rename Leon Brocard to Orange Brocard
596
597 diff --git a/AUTHORS b/AUTHORS
598 index 293dd70..722c93e 100644
599 --- a/AUTHORS
600 +++ b/AUTHORS
601 @@ -541,7 +541,7 @@ Lars Hecking <lhecking@nmrc.ucc.ie>
602 Laszlo Molnar <laszlo.molnar@eth.ericsson.se>
603 Leif Huhn <leif@hale.dkstat.com>
604 Len Johnson <lenjay@ibm.net>
605 -Leon Brocard <acme@astray.com>
606 +Orange Brocard <acme@astray.com>
607 Les Peters <lpeters@aol.net>
608 Lesley Binks <lesley.binks@gmail.com>
609 Lincoln D. Stein <lstein@cshl.org>
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610
611If you are a committer to Perl and you think the patch is good, you can
612then merge it into blead then push it out to the main repository:
613
614 % git checkout blead
615 % git merge experimental
68382b67 616 % git push origin blead
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617
618If you want to delete your temporary branch, you may do so with:
619
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620 % git checkout blead
621 % git branch -d experimental
622 error: The branch 'experimental' is not an ancestor of your current
623 HEAD. If you are sure you want to delete it, run 'git branch -D
624 experimental'.
625 % git branch -D experimental
626 Deleted branch experimental.
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627
628=head2 Committing to blead
629
630The 'blead' branch will become the next production release of Perl.
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631
632Before pushing I<any> local change to blead, it's incredibly important
633that you do a few things, lest other committers come after you with
634pitchforks and torches:
635
636=over
637
638=item *
639
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640Make sure you have a good commit message. See L<perlhack/Commit
641message> for details.
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642
643=item *
644
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645Run the test suite. You might not think that one typo fix would break a
646test file. You'd be wrong. Here's an example of where not running the
647suite caused problems. A patch was submitted that added a couple of
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648tests to an existing F<.t>. It couldn't possibly affect anything else, so
649no need to test beyond the single affected F<.t>, right? But, the
f76a37ee 650submitter's email address had changed since the last of their
04c692a8 651submissions, and this caused other tests to fail. Running the test
f76a37ee 652target given in the next item would have caught this problem.
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653
654=item *
655
656If you don't run the full test suite, at least C<make test_porting>.
657This will run basic sanity checks. To see which sanity checks, have a
658look in F<t/porting>.
659
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660=item *
661
662If you make any changes that affect miniperl or core routines that have
04baf1ff 663different code paths for miniperl, be sure to run C<make minitest>.
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664This will catch problems that even the full test suite will not catch
665because it runs a subset of tests under miniperl rather than perl.
666
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667=back
668
99cd8e46 669=head2 On merging and rebasing
961bfa8c
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670
671Simple, one-off commits pushed to the 'blead' branch should be simple
672commits that apply cleanly. In other words, you should make sure your
673work is committed against the current position of blead, so that you can
674push back to the master repository without merging.
675
676Sometimes, blead will move while you're building or testing your
677changes. When this happens, your push will be rejected with a message
678like this:
679
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680 To ssh://perl5.git.perl.org/perl.git
681 ! [rejected] blead -> blead (non-fast-forward)
682 error: failed to push some refs to 'ssh://perl5.git.perl.org/perl.git'
683 To prevent you from losing history, non-fast-forward updates were
684 rejected Merge the remote changes (e.g. 'git pull') before pushing
685 again. See the 'Note about fast-forwards' section of 'git push --help'
686 for details.
961bfa8c
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687
688When this happens, you can just I<rebase> your work against the new
689position of blead, like this (assuming your remote for the master
690repository is "p5p"):
691
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692 % git fetch p5p
693 % git rebase p5p/blead
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694
695You will see your commits being re-applied, and you will then be able to
c9d1da35 696push safely. More information about rebasing can be found in the
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697documentation for the git-rebase(1) command.
698
699For larger sets of commits that only make sense together, or that would
700benefit from a summary of the set's purpose, you should use a merge
701commit. You should perform your work on a L<topic branch|/Topic
702branches and rewriting history>, which you should regularly rebase
703against blead to ensure that your code is not broken by blead moving.
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704When you have finished your work, please perform a final rebase and
705test. Linear history is something that gets lost with every
706commit on blead, but a final rebase makes the history linear
707again, making it easier for future maintainers to see what has
708happened. Rebase as follows (assuming your work was on the
688cbe00 709branch C<< committer/somework >>):
961bfa8c 710
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711 % git checkout committer/somework
712 % git rebase blead
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713
714Then you can merge it into master like this:
715
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716 % git checkout blead
717 % git merge --no-ff --no-commit committer/somework
718 % git commit -a
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719
720The switches above deserve explanation. C<--no-ff> indicates that even
721if all your work can be applied linearly against blead, a merge commit
722should still be prepared. This ensures that all your work will be shown
723as a side branch, with all its commits merged into the mainstream blead
724by the merge commit.
725
726C<--no-commit> means that the merge commit will be I<prepared> but not
727I<committed>. The commit is then actually performed when you run the
728next command, which will bring up your editor to describe the commit.
729Without C<--no-commit>, the commit would be made with nearly no useful
730message, which would greatly diminish the value of the merge commit as a
731placeholder for the work's description.
732
733When describing the merge commit, explain the purpose of the branch, and
734keep in mind that this description will probably be used by the
735eventual release engineer when reviewing the next perldelta document.
736
04c692a8 737=head2 Committing to maintenance versions
9d68b7ed 738
77db6475
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739Maintenance versions should only be altered to add critical bug fixes,
740see L<perlpolicy>.
7f4ffa9d 741
9d68b7ed
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742To commit to a maintenance version of perl, you need to create a local
743tracking branch:
744
745 % git checkout --track -b maint-5.005 origin/maint-5.005
746
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747This creates a local branch named C<maint-5.005>, which tracks the
748remote branch C<origin/maint-5.005>. Then you can pull, commit, merge
749and push as before.
b0d36535 750
f755e97d 751You can also cherry-pick commits from blead and another branch, by
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752using the C<git cherry-pick> command. It is recommended to use the
753B<-x> option to C<git cherry-pick> in order to record the SHA1 of the
754original commit in the new commit message.
f755e97d 755
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756Before pushing any change to a maint version, make sure you've
757satisfied the steps in L</Committing to blead> above.
edcf105d 758
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759=head2 Using a smoke-me branch to test changes
760
761Sometimes a change affects code paths which you cannot test on the OSes
762which are directly available to you and it would be wise to have users
763on other OSes test the change before you commit it to blead.
764
765Fortunately, there is a way to get your change smoke-tested on various
766OSes: push it to a "smoke-me" branch and wait for certain automated
767smoke-testers to report the results from their OSes.
9b91093d 768A "smoke-me" branch is identified by the branch name: specifically, as
47ef154c 769seen on github.com it must be a local branch whose first name
9b91093d 770component is precisely C<smoke-me>.
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771
772The procedure for doing this is roughly as follows (using the example of
a3815e44 773tonyc's smoke-me branch called win32stat):
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774
775First, make a local branch and switch to it:
776
777 % git checkout -b win32stat
778
779Make some changes, build perl and test your changes, then commit them to
780your local branch. Then push your local branch to a remote smoke-me
781branch:
782
783 % git push origin win32stat:smoke-me/tonyc/win32stat
784
785Now you can switch back to blead locally:
786
787 % git checkout blead
788
789and continue working on other things while you wait a day or two,
790keeping an eye on the results reported for your smoke-me branch at
791L<http://perl.develop-help.com/?b=smoke-me/tonyc/win32state>.
792
793If all is well then update your blead branch:
794
795 % git pull
796
797then checkout your smoke-me branch once more and rebase it on blead:
798
799 % git rebase blead win32stat
800
801Now switch back to blead and merge your smoke-me branch into it:
802
803 % git checkout blead
804 % git merge win32stat
805
806As described earlier, if there are many changes on your smoke-me branch
807then you should prepare a merge commit in which to give an overview of
808those changes by using the following command instead of the last
809command above:
810
811 % git merge win32stat --no-ff --no-commit
812
813You should now build perl and test your (merged) changes one last time
814(ideally run the whole test suite, but failing that at least run the
815F<t/porting/*.t> tests) before pushing your changes as usual:
816
817 % git push origin blead
818
819Finally, you should then delete the remote smoke-me branch:
820
821 % git push origin :smoke-me/tonyc/win32stat
822
823(which is likely to produce a warning like this, which can be ignored:
824
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825 remote: fatal: ambiguous argument
826 'refs/heads/smoke-me/tonyc/win32stat':
827 unknown revision or path not in the working tree.
828 remote: Use '--' to separate paths from revisions
3afc3118
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829
830) and then delete your local branch:
831
832 % git branch -d win32stat