1git-rebase(1) 2============= 3 4NAME 5---- 6git-rebase - Reapply commits on top of another base tip 7 8SYNOPSIS 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 17DESCRIPTION 18----------- 19If <branch> is specified, 'git rebase' will perform an automatic 20`git checkout <branch>` before doing anything else. Otherwise 21it remains on the current branch. 22 23If <upstream> is not specified, the upstream configured in 24branch.<name>.remote and branch.<name>.merge options will be used (see 25linkgit:git-config[1] for details) and the `--fork-point` option is 26assumed. If you are currently not on any branch or if the current 27branch does not have a configured upstream, the rebase will abort. 28 29All changes made by commits in the current branch but that are not 30in <upstream> are saved to a temporary area. This is the same set 31of 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 33description on `--fork-point` below); or by `git log HEAD`, if the 34`--root` option is specified. 35 36The 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 39to point at the tip of the branch before the reset. 40 41The commits that were previously saved into the temporary area are 42then reapplied to the current branch, one by one, in order. Note that 43any commits in HEAD which introduce the same textual changes as a commit 44in HEAD..<upstream> are omitted (i.e., a patch already accepted upstream 45with a different commit message or timestamp will be skipped). 46 47It is possible that a merge failure will prevent this process from being 48completely automatic. You will have to resolve any such merge failure 49and run `git rebase --continue`. Another option is to bypass the commit 50that caused the merge failure with `git rebase --skip`. To check out the 51original <branch> and remove the .git/rebase-apply working files, use the 52command `git rebase --abort` instead. 53 54Assume 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 62From this point, the result of either of the following commands: 63 64 65 git rebase master 66 git rebase master topic 67 68would 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` 77followed by `git rebase master`. When rebase exits `topic` will 78remain the checked-out branch. 79 80If the upstream branch already contains a change you have made (e.g., 81because you mailed a patch which was applied upstream), then that commit 82will be skipped. For example, running `git rebase master` on the 83following history (in which `A'` and `A` introduce the same set of changes, 84but have different committer information): 85 86------------ 87 A---B---C topic 88 / 89 D---E---A'---F master 90------------ 91 92will result in: 93 94------------ 95 B'---C' topic 96 / 97 D---E---A'---F master 98------------ 99 100Here is how you would transplant a topic branch based on one 101branch to another, to pretend that you forked the topic branch 102from the latter branch, using `rebase --onto`. 103 104First let's assume your 'topic' is based on branch 'next'. 105For example, a feature developed in 'topic' depends on some 106functionality 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 116We want to make 'topic' forked from branch 'master'; for example, 117because the functionality on which 'topic' depends was merged into the 118more 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 128We can get this using the following command: 129 130 git rebase --onto master next topic 131 132 133Another example of --onto option is to rebase part of a 134branch. 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 144then the command 145 146 git rebase --onto master topicA topicB 147 148would result in: 149 150------------ 151 H'--I'--J' topicB 152 / 153 | E---F---G topicA 154 |/ 155 A---B---C---D master 156------------ 157 158This is useful when topicB does not depend on topicA. 159 160A range of commits could also be removed with rebase. If we have 161the following situation: 162 163------------ 164 E---F---G---H---I---J topicA 165------------ 166 167then the command 168 169 git rebase --onto topicA~5 topicA~3 topicA 170 171would result in the removal of commits F and G: 172 173------------ 174 E---H'---I'---J' topicA 175------------ 176 177This is useful if F and G were flawed in some way, or should not be 178part of topicA. Note that the argument to --onto and the <upstream> 179parameter can be any valid commit-ish. 180 181In case of conflict, 'git rebase' will stop at the first problematic commit 182and leave conflict markers in the tree. You can use 'git diff' to locate 183the markers (<<<<<<) and make edits to resolve the conflict. For each 184file you edit, you need to tell Git that the conflict has been resolved, 185typically this would be done with 186 187 188 git add <filename> 189 190 191After resolving the conflict manually and updating the index with the 192desired resolution, you can continue the rebasing process with 193 194 195 git rebase --continue 196 197 198Alternatively, you can undo the 'git rebase' with 199 200 201 git rebase --abort 202 203CONFIGURATION 204------------- 205 206include::rebase-config.txt[] 207 208OPTIONS 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+ 216As a special case, you may use "A\...B" as a shortcut for the 217merge base of A and B if there is exactly one merge base. You can 218leave 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+ 247See also INCOMPATIBLE OPTIONS below. 248 249--allow-empty-message:: 250 By default, rebasing commits with an empty message will fail. 251 This option overrides that behavior, allowing commits with empty 252 messages to be rebased. 253+ 254See also INCOMPATIBLE OPTIONS below. 255 256--skip:: 257 Restart the rebasing process by skipping the current patch. 258 259--edit-todo:: 260 Edit the todo list during an interactive rebase. 261 262--show-current-patch:: 263 Show the current patch in an interactive rebase or when rebase 264 is stopped because of conflicts. This is the equivalent of 265 `git show REBASE_HEAD`. 266 267-m:: 268--merge:: 269 Use merging strategies to rebase. When the recursive (default) merge 270 strategy is used, this allows rebase to be aware of renames on the 271 upstream side. 272+ 273Note that a rebase merge works by replaying each commit from the working 274branch on top of the <upstream> branch. Because of this, when a merge 275conflict happens, the side reported as 'ours' is the so-far rebased 276series, starting with <upstream>, and 'theirs' is the working branch. In 277other words, the sides are swapped. 278+ 279See also INCOMPATIBLE OPTIONS below. 280 281-s <strategy>:: 282--strategy=<strategy>:: 283 Use the given merge strategy. 284 If there is no `-s` option 'git merge-recursive' is used 285 instead. This implies --merge. 286+ 287Because 'git rebase' replays each commit from the working branch 288on top of the <upstream> branch using the given strategy, using 289the 'ours' strategy simply empties all patches from the <branch>, 290which makes little sense. 291+ 292See also INCOMPATIBLE OPTIONS below. 293 294-X <strategy-option>:: 295--strategy-option=<strategy-option>:: 296 Pass the <strategy-option> through to the merge strategy. 297 This implies `--merge` and, if no strategy has been 298 specified, `-s recursive`. Note the reversal of 'ours' and 299 'theirs' as noted above for the `-m` option. 300+ 301See also INCOMPATIBLE OPTIONS below. 302 303-S[<keyid>]:: 304--gpg-sign[=<keyid>]:: 305 GPG-sign commits. The `keyid` argument is optional and 306 defaults to the committer identity; if specified, it must be 307 stuck to the option without a space. 308 309-q:: 310--quiet:: 311 Be quiet. Implies --no-stat. 312 313-v:: 314--verbose:: 315 Be verbose. Implies --stat. 316 317--stat:: 318 Show a diffstat of what changed upstream since the last rebase. The 319 diffstat is also controlled by the configuration option rebase.stat. 320 321-n:: 322--no-stat:: 323 Do not show a diffstat as part of the rebase process. 324 325--no-verify:: 326 This option bypasses the pre-rebase hook. See also linkgit:githooks[5]. 327 328--verify:: 329 Allows the pre-rebase hook to run, which is the default. This option can 330 be used to override --no-verify. See also linkgit:githooks[5]. 331 332-C<n>:: 333 Ensure at least <n> lines of surrounding context match before 334 and after each change. When fewer lines of surrounding 335 context exist they all must match. By default no context is 336 ever ignored. 337+ 338See also INCOMPATIBLE OPTIONS below. 339 340-f:: 341--force-rebase:: 342 Force a rebase even if the current branch is up to date and 343 the command without `--force` would return without doing anything. 344+ 345You may find this (or --no-ff with an interactive rebase) helpful after 346reverting a topic branch merge, as this option recreates the topic branch with 347fresh commits so it can be remerged successfully without needing to "revert 348the reversion" (see the 349link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details). 350 351--fork-point:: 352--no-fork-point:: 353 Use reflog to find a better common ancestor between <upstream> 354 and <branch> when calculating which commits have been 355 introduced by <branch>. 356+ 357When --fork-point is active, 'fork_point' will be used instead of 358<upstream> to calculate the set of commits to rebase, where 359'fork_point' is the result of `git merge-base --fork-point <upstream> 360<branch>` command (see linkgit:git-merge-base[1]). If 'fork_point' 361ends up being empty, the <upstream> will be used as a fallback. 362+ 363If either <upstream> or --root is given on the command line, then the 364default is `--no-fork-point`, otherwise the default is `--fork-point`. 365 366--ignore-whitespace:: 367--whitespace=<option>:: 368 These flag are passed to the 'git apply' program 369 (see linkgit:git-apply[1]) that applies the patch. 370+ 371See also INCOMPATIBLE OPTIONS below. 372 373--committer-date-is-author-date:: 374--ignore-date:: 375 These flags are passed to 'git am' to easily change the dates 376 of the rebased commits (see linkgit:git-am[1]). 377+ 378See also INCOMPATIBLE OPTIONS below. 379 380--signoff:: 381 Add a Signed-off-by: trailer to all the rebased commits. Note 382 that if `--interactive` is given then only commits marked to be 383 picked, edited or reworded will have the trailer added. 384+ 385See also INCOMPATIBLE OPTIONS below. 386 387-i:: 388--interactive:: 389 Make a list of the commits which are about to be rebased. Let the 390 user edit that list before rebasing. This mode can also be used to 391 split commits (see SPLITTING COMMITS below). 392+ 393The commit list format can be changed by setting the configuration option 394rebase.instructionFormat. A customized instruction format will automatically 395have the long commit hash prepended to the format. 396+ 397See also INCOMPATIBLE OPTIONS below. 398 399-r:: 400--rebase-merges[=(rebase-cousins|no-rebase-cousins)]:: 401 By default, a rebase will simply drop merge commits from the todo 402 list, and put the rebased commits into a single, linear branch. 403 With `--rebase-merges`, the rebase will instead try to preserve 404 the branching structure within the commits that are to be rebased, 405 by recreating the merge commits. Any resolved merge conflicts or 406 manual amendments in these merge commits will have to be 407 resolved/re-applied manually. 408+ 409By default, or when `no-rebase-cousins` was specified, commits which do not 410have `<upstream>` as direct ancestor will keep their original branch point, 411i.e. commits that would be excluded by gitlink:git-log[1]'s 412`--ancestry-path` option will keep their original ancestry by default. If 413the `rebase-cousins` mode is turned on, such commits are instead rebased 414onto `<upstream>` (or `<onto>`, if specified). 415+ 416The `--rebase-merges` mode is similar in spirit to `--preserve-merges`, but 417in contrast to that option works well in interactive rebases: commits can be 418reordered, inserted and dropped at will. 419+ 420It is currently only possible to recreate the merge commits using the 421`recursive` merge strategy; Different merge strategies can be used only via 422explicit `exec git merge -s <strategy> [...]` commands. 423+ 424See also REBASING MERGES and INCOMPATIBLE OPTIONS below. 425 426-p:: 427--preserve-merges:: 428 Recreate merge commits instead of flattening the history by replaying 429 commits a merge commit introduces. Merge conflict resolutions or manual 430 amendments to merge commits are not preserved. 431+ 432This uses the `--interactive` machinery internally, but combining it 433with the `--interactive` option explicitly is generally not a good 434idea unless you know what you are doing (see BUGS below). 435+ 436See also INCOMPATIBLE OPTIONS below. 437 438-x <cmd>:: 439--exec <cmd>:: 440 Append "exec <cmd>" after each line creating a commit in the 441 final history. <cmd> will be interpreted as one or more shell 442 commands. 443+ 444You may execute several commands by either using one instance of `--exec` 445with several commands: 446+ 447 git rebase -i --exec "cmd1 && cmd2 && ..." 448+ 449or by giving more than one `--exec`: 450+ 451 git rebase -i --exec "cmd1" --exec "cmd2" --exec ... 452+ 453If `--autosquash` is used, "exec" lines will not be appended for 454the intermediate commits, and will only appear at the end of each 455squash/fixup series. 456+ 457This uses the `--interactive` machinery internally, but it can be run 458without an explicit `--interactive`. 459+ 460See also INCOMPATIBLE OPTIONS below. 461 462--root:: 463 Rebase all commits reachable from <branch>, instead of 464 limiting them with an <upstream>. This allows you to rebase 465 the root commit(s) on a branch. When used with --onto, it 466 will skip changes already contained in <newbase> (instead of 467 <upstream>) whereas without --onto it will operate on every change. 468 When used together with both --onto and --preserve-merges, 469 'all' root commits will be rewritten to have <newbase> as parent 470 instead. 471+ 472See also INCOMPATIBLE OPTIONS below. 473 474--autosquash:: 475--no-autosquash:: 476 When the commit log message begins with "squash! ..." (or 477 "fixup! ..."), and there is already a commit in the todo list that 478 matches the same `...`, automatically modify the todo list of rebase 479 -i so that the commit marked for squashing comes right after the 480 commit to be modified, and change the action of the moved commit 481 from `pick` to `squash` (or `fixup`). A commit matches the `...` if 482 the commit subject matches, or if the `...` refers to the commit's 483 hash. As a fall-back, partial matches of the commit subject work, 484 too. The recommended way to create fixup/squash commits is by using 485 the `--fixup`/`--squash` options of linkgit:git-commit[1]. 486+ 487If the `--autosquash` option is enabled by default using the 488configuration variable `rebase.autoSquash`, this option can be 489used to override and disable this setting. 490+ 491See also INCOMPATIBLE OPTIONS below. 492 493--autostash:: 494--no-autostash:: 495 Automatically create a temporary stash entry before the operation 496 begins, and apply it after the operation ends. This means 497 that you can run rebase on a dirty worktree. However, use 498 with care: the final stash application after a successful 499 rebase might result in non-trivial conflicts. 500 501--no-ff:: 502 With --interactive, cherry-pick all rebased commits instead of 503 fast-forwarding over the unchanged ones. This ensures that the 504 entire history of the rebased branch is composed of new commits. 505+ 506Without --interactive, this is a synonym for --force-rebase. 507+ 508You may find this helpful after reverting a topic branch merge, as this option 509recreates the topic branch with fresh commits so it can be remerged 510successfully without needing to "revert the reversion" (see the 511link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details). 512 513INCOMPATIBLE OPTIONS 514-------------------- 515 516git-rebase has many flags that are incompatible with each other, 517predominantly due to the fact that it has three different underlying 518implementations: 519 520 * one based on linkgit:git-am[1] (the default) 521 * one based on git-merge-recursive (merge backend) 522 * one based on linkgit:git-cherry-pick[1] (interactive backend) 523 524Flags only understood by the am backend: 525 526 * --committer-date-is-author-date 527 * --ignore-date 528 * --whitespace 529 * --ignore-whitespace 530 * -C 531 532Flags understood by both merge and interactive backends: 533 534 * --merge 535 * --strategy 536 * --strategy-option 537 * --allow-empty-message 538 539Flags only understood by the interactive backend: 540 541 * --[no-]autosquash 542 * --rebase-merges 543 * --preserve-merges 544 * --interactive 545 * --exec 546 * --keep-empty 547 * --autosquash 548 * --edit-todo 549 * --root when used in combination with --onto 550 551Other incompatible flag pairs: 552 553 * --preserve-merges and --interactive 554 * --preserve-merges and --signoff 555 * --preserve-merges and --rebase-merges 556 * --rebase-merges and --strategy 557 * --rebase-merges and --strategy-option 558 559include::merge-strategies.txt[] 560 561NOTES 562----- 563 564You should understand the implications of using 'git rebase' on a 565repository that you share. See also RECOVERING FROM UPSTREAM REBASE 566below. 567 568When the git-rebase command is run, it will first execute a "pre-rebase" 569hook if one exists. You can use this hook to do sanity checks and 570reject the rebase if it isn't appropriate. Please see the template 571pre-rebase hook script for an example. 572 573Upon completion, <branch> will be the current branch. 574 575INTERACTIVE MODE 576---------------- 577 578Rebasing interactively means that you have a chance to edit the commits 579which are rebased. You can reorder the commits, and you can 580remove them (weeding out bad or otherwise unwanted patches). 581 582The interactive mode is meant for this type of workflow: 583 5841. have a wonderful idea 5852. hack on the code 5863. prepare a series for submission 5874. submit 588 589where point 2. consists of several instances of 590 591a) regular use 592 593 1. finish something worthy of a commit 594 2. commit 595 596b) independent fixup 597 598 1. realize that something does not work 599 2. fix that 600 3. commit it 601 602Sometimes the thing fixed in b.2. cannot be amended to the not-quite 603perfect commit it fixes, because that commit is buried deeply in a 604patch series. That is exactly what interactive rebase is for: use it 605after plenty of "a"s and "b"s, by rearranging and editing 606commits, and squashing multiple commits into one. 607 608Start it with the last commit you want to retain as-is: 609 610 git rebase -i <after-this-commit> 611 612An editor will be fired up with all the commits in your current branch 613(ignoring merge commits), which come after the given commit. You can 614reorder the commits in this list to your heart's content, and you can 615remove them. The list looks more or less like this: 616 617------------------------------------------- 618pick deadbee The oneline of this commit 619pick fa1afe1 The oneline of the next commit 620... 621------------------------------------------- 622 623The oneline descriptions are purely for your pleasure; 'git rebase' will 624not look at them but at the commit names ("deadbee" and "fa1afe1" in this 625example), so do not delete or edit the names. 626 627By replacing the command "pick" with the command "edit", you can tell 628'git rebase' to stop after applying that commit, so that you can edit 629the files and/or the commit message, amend the commit, and continue 630rebasing. 631 632If you just want to edit the commit message for a commit, replace the 633command "pick" with the command "reword". 634 635To drop a commit, replace the command "pick" with "drop", or just 636delete the matching line. 637 638If you want to fold two or more commits into one, replace the command 639"pick" for the second and subsequent commits with "squash" or "fixup". 640If the commits had different authors, the folded commit will be 641attributed to the author of the first commit. The suggested commit 642message for the folded commit is the concatenation of the commit 643messages of the first commit and of those with the "squash" command, 644but omits the commit messages of commits with the "fixup" command. 645 646'git rebase' will stop when "pick" has been replaced with "edit" or 647when a command fails due to merge errors. When you are done editing 648and/or resolving conflicts you can continue with `git rebase --continue`. 649 650For example, if you want to reorder the last 5 commits, such that what 651was HEAD~4 becomes the new HEAD. To achieve that, you would call 652'git rebase' like this: 653 654---------------------- 655$ git rebase -i HEAD~5 656---------------------- 657 658And move the first patch to the end of the list. 659 660You might want to preserve merges, if you have a history like this: 661 662------------------ 663 X 664 \ 665 A---M---B 666 / 667---o---O---P---Q 668------------------ 669 670Suppose you want to rebase the side branch starting at "A" to "Q". Make 671sure that the current HEAD is "B", and call 672 673----------------------------- 674$ git rebase -i -p --onto Q O 675----------------------------- 676 677Reordering and editing commits usually creates untested intermediate 678steps. You may want to check that your history editing did not break 679anything by running a test, or at least recompiling at intermediate 680points in history by using the "exec" command (shortcut "x"). You may 681do so by creating a todo list like this one: 682 683------------------------------------------- 684pick deadbee Implement feature XXX 685fixup f1a5c00 Fix to feature XXX 686exec make 687pick c0ffeee The oneline of the next commit 688edit deadbab The oneline of the commit after 689exec cd subdir; make test 690... 691------------------------------------------- 692 693The interactive rebase will stop when a command fails (i.e. exits with 694non-0 status) to give you an opportunity to fix the problem. You can 695continue with `git rebase --continue`. 696 697The "exec" command launches the command in a shell (the one specified 698in `$SHELL`, or the default shell if `$SHELL` is not set), so you can 699use shell features (like "cd", ">", ";" ...). The command is run from 700the root of the working tree. 701 702---------------------------------- 703$ git rebase -i --exec "make test" 704---------------------------------- 705 706This command lets you check that intermediate commits are compilable. 707The todo list becomes like that: 708 709-------------------- 710pick 5928aea one 711exec make test 712pick 04d0fda two 713exec make test 714pick ba46169 three 715exec make test 716pick f4593f9 four 717exec make test 718-------------------- 719 720SPLITTING COMMITS 721----------------- 722 723In interactive mode, you can mark commits with the action "edit". However, 724this does not necessarily mean that 'git rebase' expects the result of this 725edit to be exactly one commit. Indeed, you can undo the commit, or you can 726add other commits. This can be used to split a commit into two: 727 728- Start an interactive rebase with `git rebase -i <commit>^`, where 729 <commit> is the commit you want to split. In fact, any commit range 730 will do, as long as it contains that commit. 731 732- Mark the commit you want to split with the action "edit". 733 734- When it comes to editing that commit, execute `git reset HEAD^`. The 735 effect is that the HEAD is rewound by one, and the index follows suit. 736 However, the working tree stays the same. 737 738- Now add the changes to the index that you want to have in the first 739 commit. You can use `git add` (possibly interactively) or 740 'git gui' (or both) to do that. 741 742- Commit the now-current index with whatever commit message is appropriate 743 now. 744 745- Repeat the last two steps until your working tree is clean. 746 747- Continue the rebase with `git rebase --continue`. 748 749If you are not absolutely sure that the intermediate revisions are 750consistent (they compile, pass the testsuite, etc.) you should use 751'git stash' to stash away the not-yet-committed changes 752after each commit, test, and amend the commit if fixes are necessary. 753 754 755RECOVERING FROM UPSTREAM REBASE 756------------------------------- 757 758Rebasing (or any other form of rewriting) a branch that others have 759based work on is a bad idea: anyone downstream of it is forced to 760manually fix their history. This section explains how to do the fix 761from the downstream's point of view. The real fix, however, would be 762to avoid rebasing the upstream in the first place. 763 764To illustrate, suppose you are in a situation where someone develops a 765'subsystem' branch, and you are working on a 'topic' that is dependent 766on this 'subsystem'. You might end up with a history like the 767following: 768 769------------ 770 o---o---o---o---o---o---o---o master 771 \ 772 o---o---o---o---o subsystem 773 \ 774 *---*---* topic 775------------ 776 777If 'subsystem' is rebased against 'master', the following happens: 778 779------------ 780 o---o---o---o---o---o---o---o master 781 \ \ 782 o---o---o---o---o o'--o'--o'--o'--o' subsystem 783 \ 784 *---*---* topic 785------------ 786 787If you now continue development as usual, and eventually merge 'topic' 788to 'subsystem', the commits from 'subsystem' will remain duplicated forever: 789 790------------ 791 o---o---o---o---o---o---o---o master 792 \ \ 793 o---o---o---o---o o'--o'--o'--o'--o'--M subsystem 794 \ / 795 *---*---*-..........-*--* topic 796------------ 797 798Such duplicates are generally frowned upon because they clutter up 799history, making it harder to follow. To clean things up, you need to 800transplant the commits on 'topic' to the new 'subsystem' tip, i.e., 801rebase 'topic'. This becomes a ripple effect: anyone downstream from 802'topic' is forced to rebase too, and so on! 803 804There are two kinds of fixes, discussed in the following subsections: 805 806Easy case: The changes are literally the same.:: 807 808 This happens if the 'subsystem' rebase was a simple rebase and 809 had no conflicts. 810 811Hard case: The changes are not the same.:: 812 813 This happens if the 'subsystem' rebase had conflicts, or used 814 `--interactive` to omit, edit, squash, or fixup commits; or 815 if the upstream used one of `commit --amend`, `reset`, or 816 `filter-branch`. 817 818 819The easy case 820~~~~~~~~~~~~~ 821 822Only works if the changes (patch IDs based on the diff contents) on 823'subsystem' are literally the same before and after the rebase 824'subsystem' did. 825 826In that case, the fix is easy because 'git rebase' knows to skip 827changes that are already present in the new upstream. So if you say 828(assuming you're on 'topic') 829------------ 830 $ git rebase subsystem 831------------ 832you will end up with the fixed history 833------------ 834 o---o---o---o---o---o---o---o master 835 \ 836 o'--o'--o'--o'--o' subsystem 837 \ 838 *---*---* topic 839------------ 840 841 842The hard case 843~~~~~~~~~~~~~ 844 845Things get more complicated if the 'subsystem' changes do not exactly 846correspond to the ones before the rebase. 847 848NOTE: While an "easy case recovery" sometimes appears to be successful 849 even in the hard case, it may have unintended consequences. For 850 example, a commit that was removed via `git rebase 851 --interactive` will be **resurrected**! 852 853The idea is to manually tell 'git rebase' "where the old 'subsystem' 854ended and your 'topic' began", that is, what the old merge-base 855between them was. You will have to find a way to name the last commit 856of the old 'subsystem', for example: 857 858* With the 'subsystem' reflog: after 'git fetch', the old tip of 859 'subsystem' is at `subsystem@{1}`. Subsequent fetches will 860 increase the number. (See linkgit:git-reflog[1].) 861 862* Relative to the tip of 'topic': knowing that your 'topic' has three 863 commits, the old tip of 'subsystem' must be `topic~3`. 864 865You can then transplant the old `subsystem..topic` to the new tip by 866saying (for the reflog case, and assuming you are on 'topic' already): 867------------ 868 $ git rebase --onto subsystem subsystem@{1} 869------------ 870 871The ripple effect of a "hard case" recovery is especially bad: 872'everyone' downstream from 'topic' will now have to perform a "hard 873case" recovery too! 874 875REBASING MERGES 876----------------- 877 878The interactive rebase command was originally designed to handle 879individual patch series. As such, it makes sense to exclude merge 880commits from the todo list, as the developer may have merged the 881then-current `master` while working on the branch, only to rebase 882all the commits onto `master` eventually (skipping the merge 883commits). 884 885However, there are legitimate reasons why a developer may want to 886recreate merge commits: to keep the branch structure (or "commit 887topology") when working on multiple, inter-related branches. 888 889In the following example, the developer works on a topic branch that 890refactors the way buttons are defined, and on another topic branch 891that uses that refactoring to implement a "Report a bug" button. The 892output of `git log --graph --format=%s -5` may look like this: 893 894------------ 895* Merge branch 'report-a-bug' 896|\ 897| * Add the feedback button 898* | Merge branch 'refactor-button' 899|\ \ 900| |/ 901| * Use the Button class for all buttons 902| * Extract a generic Button class from the DownloadButton one 903------------ 904 905The developer might want to rebase those commits to a newer `master` 906while keeping the branch topology, for example when the first topic 907branch is expected to be integrated into `master` much earlier than the 908second one, say, to resolve merge conflicts with changes to the 909DownloadButton class that made it into `master`. 910 911This rebase can be performed using the `--rebase-merges` option. 912It will generate a todo list looking like this: 913 914------------ 915label onto 916 917# Branch: refactor-button 918reset onto 919pick 123456 Extract a generic Button class from the DownloadButton one 920pick 654321 Use the Button class for all buttons 921label refactor-button 922 923# Branch: report-a-bug 924reset refactor-button # Use the Button class for all buttons 925pick abcdef Add the feedback button 926label report-a-bug 927 928reset onto 929merge -C a1b2c3 refactor-button # Merge 'refactor-button' 930merge -C 6f5e4d report-a-bug # Merge 'report-a-bug' 931------------ 932 933In contrast to a regular interactive rebase, there are `label`, `reset` 934and `merge` commands in addition to `pick` ones. 935 936The `label` command associates a label with the current HEAD when that 937command is executed. These labels are created as worktree-local refs 938(`refs/rewritten/<label>`) that will be deleted when the rebase 939finishes. That way, rebase operations in multiple worktrees linked to 940the same repository do not interfere with one another. If the `label` 941command fails, it is rescheduled immediately, with a helpful message how 942to proceed. 943 944The `reset` command resets the HEAD, index and worktree to the specified 945revision. It is isimilar to an `exec git reset --hard <label>`, but 946refuses to overwrite untracked files. If the `reset` command fails, it is 947rescheduled immediately, with a helpful message how to edit the todo list 948(this typically happens when a `reset` command was inserted into the todo 949list manually and contains a typo). 950 951The `merge` command will merge the specified revision into whatever is 952HEAD at that time. With `-C <original-commit>`, the commit message of 953the specified merge commit will be used. When the `-C` is changed to 954a lower-case `-c`, the message will be opened in an editor after a 955successful merge so that the user can edit the message. 956 957If a `merge` command fails for any reason other than merge conflicts (i.e. 958when the merge operation did not even start), it is rescheduled immediately. 959 960At this time, the `merge` command will *always* use the `recursive` 961merge strategy, with no way to choose a different one. To work around 962this, an `exec` command can be used to call `git merge` explicitly, 963using the fact that the labels are worktree-local refs (the ref 964`refs/rewritten/onto` would correspond to the label `onto`, for example). 965 966Note: the first command (`label onto`) labels the revision onto which 967the commits are rebased; The name `onto` is just a convention, as a nod 968to the `--onto` option. 969 970It is also possible to introduce completely new merge commits from scratch 971by adding a command of the form `merge <merge-head>`. This form will 972generate a tentative commit message and always open an editor to let the 973user edit it. This can be useful e.g. when a topic branch turns out to 974address more than a single concern and wants to be split into two or 975even more topic branches. Consider this todo list: 976 977------------ 978pick 192837 Switch from GNU Makefiles to CMake 979pick 5a6c7e Document the switch to CMake 980pick 918273 Fix detection of OpenSSL in CMake 981pick afbecd http: add support for TLS v1.3 982pick fdbaec Fix detection of cURL in CMake on Windows 983------------ 984 985The one commit in this list that is not related to CMake may very well 986have been motivated by working on fixing all those bugs introduced by 987switching to CMake, but it addresses a different concern. To split this 988branch into two topic branches, the todo list could be edited like this: 989 990------------ 991label onto 992 993pick afbecd http: add support for TLS v1.3 994label tlsv1.3 995 996reset onto 997pick 192837 Switch from GNU Makefiles to CMake 998pick 918273 Fix detection of OpenSSL in CMake 999pick fdbaec Fix detection of cURL in CMake on Windows1000pick 5a6c7e Document the switch to CMake1001label cmake10021003reset onto1004merge tlsv1.31005merge cmake1006------------10071008BUGS1009----1010The todo list presented by `--preserve-merges --interactive` does not1011represent the topology of the revision graph. Editing commits and1012rewording their commit messages should work fine, but attempts to1013reorder commits tend to produce counterintuitive results. Use1014`--rebase-merges` in such scenarios instead.10151016For example, an attempt to rearrange1017------------10181 --- 2 --- 3 --- 4 --- 51019------------1020to1021------------10221 --- 2 --- 4 --- 3 --- 51023------------1024by moving the "pick 4" line will result in the following history:1025------------1026 31027 /10281 --- 2 --- 4 --- 51029------------10301031GIT1032---1033Part of the linkgit:git[1] suite