fetch-pack: write shallow, then check connectivity
[git/git.git] / Documentation / git-rebase.txt
1 git-rebase(1)
2 =============
3
4 NAME
5 ----
6 git-rebase - Reapply commits on top of another base tip
7
8 SYNOPSIS
9 --------
10 [verse]
11 'git rebase' [-i | --interactive] [<options>] [--exec <cmd>] [--onto <newbase>]
12 [<upstream> [<branch>]]
13 'git rebase' [-i | --interactive] [<options>] [--exec <cmd>] [--onto <newbase>]
14 --root [<branch>]
15 'git rebase' --continue | --skip | --abort | --quit | --edit-todo | --show-current-patch
16
17 DESCRIPTION
18 -----------
19 If <branch> is specified, 'git rebase' will perform an automatic
20 `git checkout <branch>` before doing anything else. Otherwise
21 it remains on the current branch.
22
23 If <upstream> is not specified, the upstream configured in
24 branch.<name>.remote and branch.<name>.merge options will be used (see
25 linkgit:git-config[1] for details) and the `--fork-point` option is
26 assumed. If you are currently not on any branch or if the current
27 branch does not have a configured upstream, the rebase will abort.
28
29 All changes made by commits in the current branch but that are not
30 in <upstream> are saved to a temporary area. This is the same set
31 of commits that would be shown by `git log <upstream>..HEAD`; or by
32 `git log 'fork_point'..HEAD`, if `--fork-point` is active (see the
33 description on `--fork-point` below); or by `git log HEAD`, if the
34 `--root` option is specified.
35
36 The current branch is reset to <upstream>, or <newbase> if the
37 --onto option was supplied. This has the exact same effect as
38 `git reset --hard <upstream>` (or <newbase>). ORIG_HEAD is set
39 to point at the tip of the branch before the reset.
40
41 The commits that were previously saved into the temporary area are
42 then reapplied to the current branch, one by one, in order. Note that
43 any commits in HEAD which introduce the same textual changes as a commit
44 in HEAD..<upstream> are omitted (i.e., a patch already accepted upstream
45 with a different commit message or timestamp will be skipped).
46
47 It is possible that a merge failure will prevent this process from being
48 completely automatic. You will have to resolve any such merge failure
49 and run `git rebase --continue`. Another option is to bypass the commit
50 that caused the merge failure with `git rebase --skip`. To check out the
51 original <branch> and remove the .git/rebase-apply working files, use the
52 command `git rebase --abort` instead.
53
54 Assume the following history exists and the current branch is "topic":
55
56 ------------
57 A---B---C topic
58 /
59 D---E---F---G master
60 ------------
61
62 From this point, the result of either of the following commands:
63
64
65 git rebase master
66 git rebase master topic
67
68 would be:
69
70 ------------
71 A'--B'--C' topic
72 /
73 D---E---F---G master
74 ------------
75
76 *NOTE:* The latter form is just a short-hand of `git checkout topic`
77 followed by `git rebase master`. When rebase exits `topic` will
78 remain the checked-out branch.
79
80 If the upstream branch already contains a change you have made (e.g.,
81 because you mailed a patch which was applied upstream), then that commit
82 will be skipped. For example, running `git rebase master` on the
83 following history (in which `A'` and `A` introduce the same set of changes,
84 but have different committer information):
85
86 ------------
87 A---B---C topic
88 /
89 D---E---A'---F master
90 ------------
91
92 will result in:
93
94 ------------
95 B'---C' topic
96 /
97 D---E---A'---F master
98 ------------
99
100 Here is how you would transplant a topic branch based on one
101 branch to another, to pretend that you forked the topic branch
102 from the latter branch, using `rebase --onto`.
103
104 First let's assume your 'topic' is based on branch 'next'.
105 For example, a feature developed in 'topic' depends on some
106 functionality which is found in 'next'.
107
108 ------------
109 o---o---o---o---o master
110 \
111 o---o---o---o---o next
112 \
113 o---o---o topic
114 ------------
115
116 We want to make 'topic' forked from branch 'master'; for example,
117 because the functionality on which 'topic' depends was merged into the
118 more stable 'master' branch. We want our tree to look like this:
119
120 ------------
121 o---o---o---o---o master
122 | \
123 | o'--o'--o' topic
124 \
125 o---o---o---o---o next
126 ------------
127
128 We can get this using the following command:
129
130 git rebase --onto master next topic
131
132
133 Another example of --onto option is to rebase part of a
134 branch. If we have the following situation:
135
136 ------------
137 H---I---J topicB
138 /
139 E---F---G topicA
140 /
141 A---B---C---D master
142 ------------
143
144 then the command
145
146 git rebase --onto master topicA topicB
147
148 would result in:
149
150 ------------
151 H'--I'--J' topicB
152 /
153 | E---F---G topicA
154 |/
155 A---B---C---D master
156 ------------
157
158 This is useful when topicB does not depend on topicA.
159
160 A range of commits could also be removed with rebase. If we have
161 the following situation:
162
163 ------------
164 E---F---G---H---I---J topicA
165 ------------
166
167 then the command
168
169 git rebase --onto topicA~5 topicA~3 topicA
170
171 would result in the removal of commits F and G:
172
173 ------------
174 E---H'---I'---J' topicA
175 ------------
176
177 This is useful if F and G were flawed in some way, or should not be
178 part of topicA. Note that the argument to --onto and the <upstream>
179 parameter can be any valid commit-ish.
180
181 In case of conflict, 'git rebase' will stop at the first problematic commit
182 and leave conflict markers in the tree. You can use 'git diff' to locate
183 the markers (<<<<<<) and make edits to resolve the conflict. For each
184 file you edit, you need to tell Git that the conflict has been resolved,
185 typically this would be done with
186
187
188 git add <filename>
189
190
191 After resolving the conflict manually and updating the index with the
192 desired resolution, you can continue the rebasing process with
193
194
195 git rebase --continue
196
197
198 Alternatively, you can undo the 'git rebase' with
199
200
201 git rebase --abort
202
203 CONFIGURATION
204 -------------
205
206 include::rebase-config.txt[]
207
208 OPTIONS
209 -------
210 --onto <newbase>::
211 Starting point at which to create the new commits. If the
212 --onto option is not specified, the starting point is
213 <upstream>. May be any valid commit, and not just an
214 existing branch name.
215 +
216 As a special case, you may use "A\...B" as a shortcut for the
217 merge base of A and B if there is exactly one merge base. You can
218 leave out at most one of A and B, in which case it defaults to HEAD.
219
220 <upstream>::
221 Upstream branch to compare against. May be any valid commit,
222 not just an existing branch name. Defaults to the configured
223 upstream for the current branch.
224
225 <branch>::
226 Working branch; defaults to HEAD.
227
228 --continue::
229 Restart the rebasing process after having resolved a merge conflict.
230
231 --abort::
232 Abort the rebase operation and reset HEAD to the original
233 branch. If <branch> was provided when the rebase operation was
234 started, then HEAD will be reset to <branch>. Otherwise HEAD
235 will be reset to where it was when the rebase operation was
236 started.
237
238 --quit::
239 Abort the rebase operation but HEAD is not reset back to the
240 original branch. The index and working tree are also left
241 unchanged as a result.
242
243 --keep-empty::
244 Keep the commits that do not change anything from its
245 parents in the result.
246
247 --allow-empty-message::
248 By default, rebasing commits with an empty message will fail.
249 This option overrides that behavior, allowing commits with empty
250 messages to be rebased.
251
252 --skip::
253 Restart the rebasing process by skipping the current patch.
254
255 --edit-todo::
256 Edit the todo list during an interactive rebase.
257
258 --show-current-patch::
259 Show the current patch in an interactive rebase or when rebase
260 is stopped because of conflicts. This is the equivalent of
261 `git show REBASE_HEAD`.
262
263 -m::
264 --merge::
265 Use merging strategies to rebase. When the recursive (default) merge
266 strategy is used, this allows rebase to be aware of renames on the
267 upstream side.
268 +
269 Note that a rebase merge works by replaying each commit from the working
270 branch on top of the <upstream> branch. Because of this, when a merge
271 conflict happens, the side reported as 'ours' is the so-far rebased
272 series, starting with <upstream>, and 'theirs' is the working branch. In
273 other words, the sides are swapped.
274
275 -s <strategy>::
276 --strategy=<strategy>::
277 Use the given merge strategy.
278 If there is no `-s` option 'git merge-recursive' is used
279 instead. This implies --merge.
280 +
281 Because 'git rebase' replays each commit from the working branch
282 on top of the <upstream> branch using the given strategy, using
283 the 'ours' strategy simply discards all patches from the <branch>,
284 which makes little sense.
285
286 -X <strategy-option>::
287 --strategy-option=<strategy-option>::
288 Pass the <strategy-option> through to the merge strategy.
289 This implies `--merge` and, if no strategy has been
290 specified, `-s recursive`. Note the reversal of 'ours' and
291 'theirs' as noted above for the `-m` option.
292
293 -S[<keyid>]::
294 --gpg-sign[=<keyid>]::
295 GPG-sign commits. The `keyid` argument is optional and
296 defaults to the committer identity; if specified, it must be
297 stuck to the option without a space.
298
299 -q::
300 --quiet::
301 Be quiet. Implies --no-stat.
302
303 -v::
304 --verbose::
305 Be verbose. Implies --stat.
306
307 --stat::
308 Show a diffstat of what changed upstream since the last rebase. The
309 diffstat is also controlled by the configuration option rebase.stat.
310
311 -n::
312 --no-stat::
313 Do not show a diffstat as part of the rebase process.
314
315 --no-verify::
316 This option bypasses the pre-rebase hook. See also linkgit:githooks[5].
317
318 --verify::
319 Allows the pre-rebase hook to run, which is the default. This option can
320 be used to override --no-verify. See also linkgit:githooks[5].
321
322 -C<n>::
323 Ensure at least <n> lines of surrounding context match before
324 and after each change. When fewer lines of surrounding
325 context exist they all must match. By default no context is
326 ever ignored.
327
328 -f::
329 --force-rebase::
330 Force a rebase even if the current branch is up to date and
331 the command without `--force` would return without doing anything.
332 +
333 You may find this (or --no-ff with an interactive rebase) helpful after
334 reverting a topic branch merge, as this option recreates the topic branch with
335 fresh commits so it can be remerged successfully without needing to "revert
336 the reversion" (see the
337 link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details).
338
339 --fork-point::
340 --no-fork-point::
341 Use reflog to find a better common ancestor between <upstream>
342 and <branch> when calculating which commits have been
343 introduced by <branch>.
344 +
345 When --fork-point is active, 'fork_point' will be used instead of
346 <upstream> to calculate the set of commits to rebase, where
347 'fork_point' is the result of `git merge-base --fork-point <upstream>
348 <branch>` command (see linkgit:git-merge-base[1]). If 'fork_point'
349 ends up being empty, the <upstream> will be used as a fallback.
350 +
351 If either <upstream> or --root is given on the command line, then the
352 default is `--no-fork-point`, otherwise the default is `--fork-point`.
353
354 --ignore-whitespace::
355 --whitespace=<option>::
356 These flag are passed to the 'git apply' program
357 (see linkgit:git-apply[1]) that applies the patch.
358 Incompatible with the --interactive option.
359
360 --committer-date-is-author-date::
361 --ignore-date::
362 These flags are passed to 'git am' to easily change the dates
363 of the rebased commits (see linkgit:git-am[1]).
364 Incompatible with the --interactive option.
365
366 --signoff::
367 Add a Signed-off-by: trailer to all the rebased commits. Note
368 that if `--interactive` is given then only commits marked to be
369 picked, edited or reworded will have the trailer added. Incompatible
370 with the `--preserve-merges` option.
371
372 -i::
373 --interactive::
374 Make a list of the commits which are about to be rebased. Let the
375 user edit that list before rebasing. This mode can also be used to
376 split commits (see SPLITTING COMMITS below).
377 +
378 The commit list format can be changed by setting the configuration option
379 rebase.instructionFormat. A customized instruction format will automatically
380 have the long commit hash prepended to the format.
381
382 -r::
383 --rebase-merges[=(rebase-cousins|no-rebase-cousins)]::
384 By default, a rebase will simply drop merge commits from the todo
385 list, and put the rebased commits into a single, linear branch.
386 With `--rebase-merges`, the rebase will instead try to preserve
387 the branching structure within the commits that are to be rebased,
388 by recreating the merge commits. Any resolved merge conflicts or
389 manual amendments in these merge commits will have to be
390 resolved/re-applied manually.
391 +
392 By default, or when `no-rebase-cousins` was specified, commits which do not
393 have `<upstream>` as direct ancestor will keep their original branch point,
394 i.e. commits that would be excluded by gitlink:git-log[1]'s
395 `--ancestry-path` option will keep their original ancestry by default. If
396 the `rebase-cousins` mode is turned on, such commits are instead rebased
397 onto `<upstream>` (or `<onto>`, if specified).
398 +
399 The `--rebase-merges` mode is similar in spirit to `--preserve-merges`, but
400 in contrast to that option works well in interactive rebases: commits can be
401 reordered, inserted and dropped at will.
402 +
403 It is currently only possible to recreate the merge commits using the
404 `recursive` merge strategy; Different merge strategies can be used only via
405 explicit `exec git merge -s <strategy> [...]` commands.
406 +
407 See also REBASING MERGES below.
408
409 -p::
410 --preserve-merges::
411 Recreate merge commits instead of flattening the history by replaying
412 commits a merge commit introduces. Merge conflict resolutions or manual
413 amendments to merge commits are not preserved.
414 +
415 This uses the `--interactive` machinery internally, but combining it
416 with the `--interactive` option explicitly is generally not a good
417 idea unless you know what you are doing (see BUGS below).
418
419 -x <cmd>::
420 --exec <cmd>::
421 Append "exec <cmd>" after each line creating a commit in the
422 final history. <cmd> will be interpreted as one or more shell
423 commands.
424 +
425 You may execute several commands by either using one instance of `--exec`
426 with several commands:
427 +
428 git rebase -i --exec "cmd1 && cmd2 && ..."
429 +
430 or by giving more than one `--exec`:
431 +
432 git rebase -i --exec "cmd1" --exec "cmd2" --exec ...
433 +
434 If `--autosquash` is used, "exec" lines will not be appended for
435 the intermediate commits, and will only appear at the end of each
436 squash/fixup series.
437 +
438 This uses the `--interactive` machinery internally, but it can be run
439 without an explicit `--interactive`.
440
441 --root::
442 Rebase all commits reachable from <branch>, instead of
443 limiting them with an <upstream>. This allows you to rebase
444 the root commit(s) on a branch. When used with --onto, it
445 will skip changes already contained in <newbase> (instead of
446 <upstream>) whereas without --onto it will operate on every change.
447 When used together with both --onto and --preserve-merges,
448 'all' root commits will be rewritten to have <newbase> as parent
449 instead.
450
451 --autosquash::
452 --no-autosquash::
453 When the commit log message begins with "squash! ..." (or
454 "fixup! ..."), and there is already a commit in the todo list that
455 matches the same `...`, automatically modify the todo list of rebase
456 -i so that the commit marked for squashing comes right after the
457 commit to be modified, and change the action of the moved commit
458 from `pick` to `squash` (or `fixup`). A commit matches the `...` if
459 the commit subject matches, or if the `...` refers to the commit's
460 hash. As a fall-back, partial matches of the commit subject work,
461 too. The recommended way to create fixup/squash commits is by using
462 the `--fixup`/`--squash` options of linkgit:git-commit[1].
463 +
464 This option is only valid when the `--interactive` option is used.
465 +
466 If the `--autosquash` option is enabled by default using the
467 configuration variable `rebase.autoSquash`, this option can be
468 used to override and disable this setting.
469
470 --autostash::
471 --no-autostash::
472 Automatically create a temporary stash entry before the operation
473 begins, and apply it after the operation ends. This means
474 that you can run rebase on a dirty worktree. However, use
475 with care: the final stash application after a successful
476 rebase might result in non-trivial conflicts.
477
478 --no-ff::
479 With --interactive, cherry-pick all rebased commits instead of
480 fast-forwarding over the unchanged ones. This ensures that the
481 entire history of the rebased branch is composed of new commits.
482 +
483 Without --interactive, this is a synonym for --force-rebase.
484 +
485 You may find this helpful after reverting a topic branch merge, as this option
486 recreates the topic branch with fresh commits so it can be remerged
487 successfully without needing to "revert the reversion" (see the
488 link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details).
489
490 include::merge-strategies.txt[]
491
492 NOTES
493 -----
494
495 You should understand the implications of using 'git rebase' on a
496 repository that you share. See also RECOVERING FROM UPSTREAM REBASE
497 below.
498
499 When the git-rebase command is run, it will first execute a "pre-rebase"
500 hook if one exists. You can use this hook to do sanity checks and
501 reject the rebase if it isn't appropriate. Please see the template
502 pre-rebase hook script for an example.
503
504 Upon completion, <branch> will be the current branch.
505
506 INTERACTIVE MODE
507 ----------------
508
509 Rebasing interactively means that you have a chance to edit the commits
510 which are rebased. You can reorder the commits, and you can
511 remove them (weeding out bad or otherwise unwanted patches).
512
513 The interactive mode is meant for this type of workflow:
514
515 1. have a wonderful idea
516 2. hack on the code
517 3. prepare a series for submission
518 4. submit
519
520 where point 2. consists of several instances of
521
522 a) regular use
523
524 1. finish something worthy of a commit
525 2. commit
526
527 b) independent fixup
528
529 1. realize that something does not work
530 2. fix that
531 3. commit it
532
533 Sometimes the thing fixed in b.2. cannot be amended to the not-quite
534 perfect commit it fixes, because that commit is buried deeply in a
535 patch series. That is exactly what interactive rebase is for: use it
536 after plenty of "a"s and "b"s, by rearranging and editing
537 commits, and squashing multiple commits into one.
538
539 Start it with the last commit you want to retain as-is:
540
541 git rebase -i <after-this-commit>
542
543 An editor will be fired up with all the commits in your current branch
544 (ignoring merge commits), which come after the given commit. You can
545 reorder the commits in this list to your heart's content, and you can
546 remove them. The list looks more or less like this:
547
548 -------------------------------------------
549 pick deadbee The oneline of this commit
550 pick fa1afe1 The oneline of the next commit
551 ...
552 -------------------------------------------
553
554 The oneline descriptions are purely for your pleasure; 'git rebase' will
555 not look at them but at the commit names ("deadbee" and "fa1afe1" in this
556 example), so do not delete or edit the names.
557
558 By replacing the command "pick" with the command "edit", you can tell
559 'git rebase' to stop after applying that commit, so that you can edit
560 the files and/or the commit message, amend the commit, and continue
561 rebasing.
562
563 If you just want to edit the commit message for a commit, replace the
564 command "pick" with the command "reword".
565
566 To drop a commit, replace the command "pick" with "drop", or just
567 delete the matching line.
568
569 If you want to fold two or more commits into one, replace the command
570 "pick" for the second and subsequent commits with "squash" or "fixup".
571 If the commits had different authors, the folded commit will be
572 attributed to the author of the first commit. The suggested commit
573 message for the folded commit is the concatenation of the commit
574 messages of the first commit and of those with the "squash" command,
575 but omits the commit messages of commits with the "fixup" command.
576
577 'git rebase' will stop when "pick" has been replaced with "edit" or
578 when a command fails due to merge errors. When you are done editing
579 and/or resolving conflicts you can continue with `git rebase --continue`.
580
581 For example, if you want to reorder the last 5 commits, such that what
582 was HEAD~4 becomes the new HEAD. To achieve that, you would call
583 'git rebase' like this:
584
585 ----------------------
586 $ git rebase -i HEAD~5
587 ----------------------
588
589 And move the first patch to the end of the list.
590
591 You might want to preserve merges, if you have a history like this:
592
593 ------------------
594 X
595 \
596 A---M---B
597 /
598 ---o---O---P---Q
599 ------------------
600
601 Suppose you want to rebase the side branch starting at "A" to "Q". Make
602 sure that the current HEAD is "B", and call
603
604 -----------------------------
605 $ git rebase -i -p --onto Q O
606 -----------------------------
607
608 Reordering and editing commits usually creates untested intermediate
609 steps. You may want to check that your history editing did not break
610 anything by running a test, or at least recompiling at intermediate
611 points in history by using the "exec" command (shortcut "x"). You may
612 do so by creating a todo list like this one:
613
614 -------------------------------------------
615 pick deadbee Implement feature XXX
616 fixup f1a5c00 Fix to feature XXX
617 exec make
618 pick c0ffeee The oneline of the next commit
619 edit deadbab The oneline of the commit after
620 exec cd subdir; make test
621 ...
622 -------------------------------------------
623
624 The interactive rebase will stop when a command fails (i.e. exits with
625 non-0 status) to give you an opportunity to fix the problem. You can
626 continue with `git rebase --continue`.
627
628 The "exec" command launches the command in a shell (the one specified
629 in `$SHELL`, or the default shell if `$SHELL` is not set), so you can
630 use shell features (like "cd", ">", ";" ...). The command is run from
631 the root of the working tree.
632
633 ----------------------------------
634 $ git rebase -i --exec "make test"
635 ----------------------------------
636
637 This command lets you check that intermediate commits are compilable.
638 The todo list becomes like that:
639
640 --------------------
641 pick 5928aea one
642 exec make test
643 pick 04d0fda two
644 exec make test
645 pick ba46169 three
646 exec make test
647 pick f4593f9 four
648 exec make test
649 --------------------
650
651 SPLITTING COMMITS
652 -----------------
653
654 In interactive mode, you can mark commits with the action "edit". However,
655 this does not necessarily mean that 'git rebase' expects the result of this
656 edit to be exactly one commit. Indeed, you can undo the commit, or you can
657 add other commits. This can be used to split a commit into two:
658
659 - Start an interactive rebase with `git rebase -i <commit>^`, where
660 <commit> is the commit you want to split. In fact, any commit range
661 will do, as long as it contains that commit.
662
663 - Mark the commit you want to split with the action "edit".
664
665 - When it comes to editing that commit, execute `git reset HEAD^`. The
666 effect is that the HEAD is rewound by one, and the index follows suit.
667 However, the working tree stays the same.
668
669 - Now add the changes to the index that you want to have in the first
670 commit. You can use `git add` (possibly interactively) or
671 'git gui' (or both) to do that.
672
673 - Commit the now-current index with whatever commit message is appropriate
674 now.
675
676 - Repeat the last two steps until your working tree is clean.
677
678 - Continue the rebase with `git rebase --continue`.
679
680 If you are not absolutely sure that the intermediate revisions are
681 consistent (they compile, pass the testsuite, etc.) you should use
682 'git stash' to stash away the not-yet-committed changes
683 after each commit, test, and amend the commit if fixes are necessary.
684
685
686 RECOVERING FROM UPSTREAM REBASE
687 -------------------------------
688
689 Rebasing (or any other form of rewriting) a branch that others have
690 based work on is a bad idea: anyone downstream of it is forced to
691 manually fix their history. This section explains how to do the fix
692 from the downstream's point of view. The real fix, however, would be
693 to avoid rebasing the upstream in the first place.
694
695 To illustrate, suppose you are in a situation where someone develops a
696 'subsystem' branch, and you are working on a 'topic' that is dependent
697 on this 'subsystem'. You might end up with a history like the
698 following:
699
700 ------------
701 o---o---o---o---o---o---o---o master
702 \
703 o---o---o---o---o subsystem
704 \
705 *---*---* topic
706 ------------
707
708 If 'subsystem' is rebased against 'master', the following happens:
709
710 ------------
711 o---o---o---o---o---o---o---o master
712 \ \
713 o---o---o---o---o o'--o'--o'--o'--o' subsystem
714 \
715 *---*---* topic
716 ------------
717
718 If you now continue development as usual, and eventually merge 'topic'
719 to 'subsystem', the commits from 'subsystem' will remain duplicated forever:
720
721 ------------
722 o---o---o---o---o---o---o---o master
723 \ \
724 o---o---o---o---o o'--o'--o'--o'--o'--M subsystem
725 \ /
726 *---*---*-..........-*--* topic
727 ------------
728
729 Such duplicates are generally frowned upon because they clutter up
730 history, making it harder to follow. To clean things up, you need to
731 transplant the commits on 'topic' to the new 'subsystem' tip, i.e.,
732 rebase 'topic'. This becomes a ripple effect: anyone downstream from
733 'topic' is forced to rebase too, and so on!
734
735 There are two kinds of fixes, discussed in the following subsections:
736
737 Easy case: The changes are literally the same.::
738
739 This happens if the 'subsystem' rebase was a simple rebase and
740 had no conflicts.
741
742 Hard case: The changes are not the same.::
743
744 This happens if the 'subsystem' rebase had conflicts, or used
745 `--interactive` to omit, edit, squash, or fixup commits; or
746 if the upstream used one of `commit --amend`, `reset`, or
747 `filter-branch`.
748
749
750 The easy case
751 ~~~~~~~~~~~~~
752
753 Only works if the changes (patch IDs based on the diff contents) on
754 'subsystem' are literally the same before and after the rebase
755 'subsystem' did.
756
757 In that case, the fix is easy because 'git rebase' knows to skip
758 changes that are already present in the new upstream. So if you say
759 (assuming you're on 'topic')
760 ------------
761 $ git rebase subsystem
762 ------------
763 you will end up with the fixed history
764 ------------
765 o---o---o---o---o---o---o---o master
766 \
767 o'--o'--o'--o'--o' subsystem
768 \
769 *---*---* topic
770 ------------
771
772
773 The hard case
774 ~~~~~~~~~~~~~
775
776 Things get more complicated if the 'subsystem' changes do not exactly
777 correspond to the ones before the rebase.
778
779 NOTE: While an "easy case recovery" sometimes appears to be successful
780 even in the hard case, it may have unintended consequences. For
781 example, a commit that was removed via `git rebase
782 --interactive` will be **resurrected**!
783
784 The idea is to manually tell 'git rebase' "where the old 'subsystem'
785 ended and your 'topic' began", that is, what the old merge-base
786 between them was. You will have to find a way to name the last commit
787 of the old 'subsystem', for example:
788
789 * With the 'subsystem' reflog: after 'git fetch', the old tip of
790 'subsystem' is at `subsystem@{1}`. Subsequent fetches will
791 increase the number. (See linkgit:git-reflog[1].)
792
793 * Relative to the tip of 'topic': knowing that your 'topic' has three
794 commits, the old tip of 'subsystem' must be `topic~3`.
795
796 You can then transplant the old `subsystem..topic` to the new tip by
797 saying (for the reflog case, and assuming you are on 'topic' already):
798 ------------
799 $ git rebase --onto subsystem subsystem@{1}
800 ------------
801
802 The ripple effect of a "hard case" recovery is especially bad:
803 'everyone' downstream from 'topic' will now have to perform a "hard
804 case" recovery too!
805
806 REBASING MERGES
807 -----------------
808
809 The interactive rebase command was originally designed to handle
810 individual patch series. As such, it makes sense to exclude merge
811 commits from the todo list, as the developer may have merged the
812 then-current `master` while working on the branch, only to rebase
813 all the commits onto `master` eventually (skipping the merge
814 commits).
815
816 However, there are legitimate reasons why a developer may want to
817 recreate merge commits: to keep the branch structure (or "commit
818 topology") when working on multiple, inter-related branches.
819
820 In the following example, the developer works on a topic branch that
821 refactors the way buttons are defined, and on another topic branch
822 that uses that refactoring to implement a "Report a bug" button. The
823 output of `git log --graph --format=%s -5` may look like this:
824
825 ------------
826 * Merge branch 'report-a-bug'
827 |\
828 | * Add the feedback button
829 * | Merge branch 'refactor-button'
830 |\ \
831 | |/
832 | * Use the Button class for all buttons
833 | * Extract a generic Button class from the DownloadButton one
834 ------------
835
836 The developer might want to rebase those commits to a newer `master`
837 while keeping the branch topology, for example when the first topic
838 branch is expected to be integrated into `master` much earlier than the
839 second one, say, to resolve merge conflicts with changes to the
840 DownloadButton class that made it into `master`.
841
842 This rebase can be performed using the `--rebase-merges` option.
843 It will generate a todo list looking like this:
844
845 ------------
846 label onto
847
848 # Branch: refactor-button
849 reset onto
850 pick 123456 Extract a generic Button class from the DownloadButton one
851 pick 654321 Use the Button class for all buttons
852 label refactor-button
853
854 # Branch: report-a-bug
855 reset refactor-button # Use the Button class for all buttons
856 pick abcdef Add the feedback button
857 label report-a-bug
858
859 reset onto
860 merge -C a1b2c3 refactor-button # Merge 'refactor-button'
861 merge -C 6f5e4d report-a-bug # Merge 'report-a-bug'
862 ------------
863
864 In contrast to a regular interactive rebase, there are `label`, `reset`
865 and `merge` commands in addition to `pick` ones.
866
867 The `label` command associates a label with the current HEAD when that
868 command is executed. These labels are created as worktree-local refs
869 (`refs/rewritten/<label>`) that will be deleted when the rebase
870 finishes. That way, rebase operations in multiple worktrees linked to
871 the same repository do not interfere with one another. If the `label`
872 command fails, it is rescheduled immediately, with a helpful message how
873 to proceed.
874
875 The `reset` command resets the HEAD, index and worktree to the specified
876 revision. It is isimilar to an `exec git reset --hard <label>`, but
877 refuses to overwrite untracked files. If the `reset` command fails, it is
878 rescheduled immediately, with a helpful message how to edit the todo list
879 (this typically happens when a `reset` command was inserted into the todo
880 list manually and contains a typo).
881
882 The `merge` command will merge the specified revision into whatever is
883 HEAD at that time. With `-C <original-commit>`, the commit message of
884 the specified merge commit will be used. When the `-C` is changed to
885 a lower-case `-c`, the message will be opened in an editor after a
886 successful merge so that the user can edit the message.
887
888 If a `merge` command fails for any reason other than merge conflicts (i.e.
889 when the merge operation did not even start), it is rescheduled immediately.
890
891 At this time, the `merge` command will *always* use the `recursive`
892 merge strategy, with no way to choose a different one. To work around
893 this, an `exec` command can be used to call `git merge` explicitly,
894 using the fact that the labels are worktree-local refs (the ref
895 `refs/rewritten/onto` would correspond to the label `onto`, for example).
896
897 Note: the first command (`label onto`) labels the revision onto which
898 the commits are rebased; The name `onto` is just a convention, as a nod
899 to the `--onto` option.
900
901 It is also possible to introduce completely new merge commits from scratch
902 by adding a command of the form `merge <merge-head>`. This form will
903 generate a tentative commit message and always open an editor to let the
904 user edit it. This can be useful e.g. when a topic branch turns out to
905 address more than a single concern and wants to be split into two or
906 even more topic branches. Consider this todo list:
907
908 ------------
909 pick 192837 Switch from GNU Makefiles to CMake
910 pick 5a6c7e Document the switch to CMake
911 pick 918273 Fix detection of OpenSSL in CMake
912 pick afbecd http: add support for TLS v1.3
913 pick fdbaec Fix detection of cURL in CMake on Windows
914 ------------
915
916 The one commit in this list that is not related to CMake may very well
917 have been motivated by working on fixing all those bugs introduced by
918 switching to CMake, but it addresses a different concern. To split this
919 branch into two topic branches, the todo list could be edited like this:
920
921 ------------
922 label onto
923
924 pick afbecd http: add support for TLS v1.3
925 label tlsv1.3
926
927 reset onto
928 pick 192837 Switch from GNU Makefiles to CMake
929 pick 918273 Fix detection of OpenSSL in CMake
930 pick fdbaec Fix detection of cURL in CMake on Windows
931 pick 5a6c7e Document the switch to CMake
932 label cmake
933
934 reset onto
935 merge tlsv1.3
936 merge cmake
937 ------------
938
939 BUGS
940 ----
941 The todo list presented by `--preserve-merges --interactive` does not
942 represent the topology of the revision graph. Editing commits and
943 rewording their commit messages should work fine, but attempts to
944 reorder commits tend to produce counterintuitive results. Use
945 `--rebase-merges` in such scenarios instead.
946
947 For example, an attempt to rearrange
948 ------------
949 1 --- 2 --- 3 --- 4 --- 5
950 ------------
951 to
952 ------------
953 1 --- 2 --- 4 --- 3 --- 5
954 ------------
955 by moving the "pick 4" line will result in the following history:
956 ------------
957 3
958 /
959 1 --- 2 --- 4 --- 5
960 ------------
961
962 GIT
963 ---
964 Part of the linkgit:git[1] suite