7ef95774726ddaefeede9474e8c66e27b98ddaa6
   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
 247--skip::
 248        Restart the rebasing process by skipping the current patch.
 249
 250--edit-todo::
 251        Edit the todo list during an interactive rebase.
 252
 253--show-current-patch::
 254        Show the current patch in an interactive rebase or when rebase
 255        is stopped because of conflicts.
 256
 257-m::
 258--merge::
 259        Use merging strategies to rebase.  When the recursive (default) merge
 260        strategy is used, this allows rebase to be aware of renames on the
 261        upstream side.
 262+
 263Note that a rebase merge works by replaying each commit from the working
 264branch on top of the <upstream> branch.  Because of this, when a merge
 265conflict happens, the side reported as 'ours' is the so-far rebased
 266series, starting with <upstream>, and 'theirs' is the working branch.  In
 267other words, the sides are swapped.
 268
 269-s <strategy>::
 270--strategy=<strategy>::
 271        Use the given merge strategy.
 272        If there is no `-s` option 'git merge-recursive' is used
 273        instead.  This implies --merge.
 274+
 275Because 'git rebase' replays each commit from the working branch
 276on top of the <upstream> branch using the given strategy, using
 277the 'ours' strategy simply discards all patches from the <branch>,
 278which makes little sense.
 279
 280-X <strategy-option>::
 281--strategy-option=<strategy-option>::
 282        Pass the <strategy-option> through to the merge strategy.
 283        This implies `--merge` and, if no strategy has been
 284        specified, `-s recursive`.  Note the reversal of 'ours' and
 285        'theirs' as noted above for the `-m` option.
 286
 287-S[<keyid>]::
 288--gpg-sign[=<keyid>]::
 289        GPG-sign commits. The `keyid` argument is optional and
 290        defaults to the committer identity; if specified, it must be
 291        stuck to the option without a space.
 292
 293-q::
 294--quiet::
 295        Be quiet. Implies --no-stat.
 296
 297-v::
 298--verbose::
 299        Be verbose. Implies --stat.
 300
 301--stat::
 302        Show a diffstat of what changed upstream since the last rebase. The
 303        diffstat is also controlled by the configuration option rebase.stat.
 304
 305-n::
 306--no-stat::
 307        Do not show a diffstat as part of the rebase process.
 308
 309--no-verify::
 310        This option bypasses the pre-rebase hook.  See also linkgit:githooks[5].
 311
 312--verify::
 313        Allows the pre-rebase hook to run, which is the default.  This option can
 314        be used to override --no-verify.  See also linkgit:githooks[5].
 315
 316-C<n>::
 317        Ensure at least <n> lines of surrounding context match before
 318        and after each change.  When fewer lines of surrounding
 319        context exist they all must match.  By default no context is
 320        ever ignored.
 321
 322-f::
 323--force-rebase::
 324        Force a rebase even if the current branch is up to date and
 325        the command without `--force` would return without doing anything.
 326+
 327You may find this (or --no-ff with an interactive rebase) helpful after
 328reverting a topic branch merge, as this option recreates the topic branch with
 329fresh commits so it can be remerged successfully without needing to "revert
 330the reversion" (see the
 331link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details).
 332
 333--fork-point::
 334--no-fork-point::
 335        Use reflog to find a better common ancestor between <upstream>
 336        and <branch> when calculating which commits have been
 337        introduced by <branch>.
 338+
 339When --fork-point is active, 'fork_point' will be used instead of
 340<upstream> to calculate the set of commits to rebase, where
 341'fork_point' is the result of `git merge-base --fork-point <upstream>
 342<branch>` command (see linkgit:git-merge-base[1]).  If 'fork_point'
 343ends up being empty, the <upstream> will be used as a fallback.
 344+
 345If either <upstream> or --root is given on the command line, then the
 346default is `--no-fork-point`, otherwise the default is `--fork-point`.
 347
 348--ignore-whitespace::
 349--whitespace=<option>::
 350        These flag are passed to the 'git apply' program
 351        (see linkgit:git-apply[1]) that applies the patch.
 352        Incompatible with the --interactive option.
 353
 354--committer-date-is-author-date::
 355--ignore-date::
 356        These flags are passed to 'git am' to easily change the dates
 357        of the rebased commits (see linkgit:git-am[1]).
 358        Incompatible with the --interactive option.
 359
 360--signoff::
 361        This flag is passed to 'git am' to sign off all the rebased
 362        commits (see linkgit:git-am[1]). Incompatible with the
 363        --interactive option.
 364
 365-i::
 366--interactive::
 367        Make a list of the commits which are about to be rebased.  Let the
 368        user edit that list before rebasing.  This mode can also be used to
 369        split commits (see SPLITTING COMMITS below).
 370+
 371The commit list format can be changed by setting the configuration option
 372rebase.instructionFormat.  A customized instruction format will automatically
 373have the long commit hash prepended to the format.
 374
 375-p::
 376--preserve-merges::
 377        Recreate merge commits instead of flattening the history by replaying
 378        commits a merge commit introduces. Merge conflict resolutions or manual
 379        amendments to merge commits are not preserved.
 380+
 381This uses the `--interactive` machinery internally, but combining it
 382with the `--interactive` option explicitly is generally not a good
 383idea unless you know what you are doing (see BUGS below).
 384
 385-x <cmd>::
 386--exec <cmd>::
 387        Append "exec <cmd>" after each line creating a commit in the
 388        final history. <cmd> will be interpreted as one or more shell
 389        commands.
 390+
 391You may execute several commands by either using one instance of `--exec`
 392with several commands:
 393+
 394        git rebase -i --exec "cmd1 && cmd2 && ..."
 395+
 396or by giving more than one `--exec`:
 397+
 398        git rebase -i --exec "cmd1" --exec "cmd2" --exec ...
 399+
 400If `--autosquash` is used, "exec" lines will not be appended for
 401the intermediate commits, and will only appear at the end of each
 402squash/fixup series.
 403+
 404This uses the `--interactive` machinery internally, but it can be run
 405without an explicit `--interactive`.
 406
 407--root::
 408        Rebase all commits reachable from <branch>, instead of
 409        limiting them with an <upstream>.  This allows you to rebase
 410        the root commit(s) on a branch.  When used with --onto, it
 411        will skip changes already contained in <newbase> (instead of
 412        <upstream>) whereas without --onto it will operate on every change.
 413        When used together with both --onto and --preserve-merges,
 414        'all' root commits will be rewritten to have <newbase> as parent
 415        instead.
 416
 417--autosquash::
 418--no-autosquash::
 419        When the commit log message begins with "squash! ..." (or
 420        "fixup! ..."), and there is already a commit in the todo list that
 421        matches the same `...`, automatically modify the todo list of rebase
 422        -i so that the commit marked for squashing comes right after the
 423        commit to be modified, and change the action of the moved commit
 424        from `pick` to `squash` (or `fixup`).  A commit matches the `...` if
 425        the commit subject matches, or if the `...` refers to the commit's
 426        hash. As a fall-back, partial matches of the commit subject work,
 427        too.  The recommended way to create fixup/squash commits is by using
 428        the `--fixup`/`--squash` options of linkgit:git-commit[1].
 429+
 430This option is only valid when the `--interactive` option is used.
 431+
 432If the `--autosquash` option is enabled by default using the
 433configuration variable `rebase.autoSquash`, this option can be
 434used to override and disable this setting.
 435
 436--autostash::
 437--no-autostash::
 438        Automatically create a temporary stash entry before the operation
 439        begins, and apply it after the operation ends.  This means
 440        that you can run rebase on a dirty worktree.  However, use
 441        with care: the final stash application after a successful
 442        rebase might result in non-trivial conflicts.
 443
 444--no-ff::
 445        With --interactive, cherry-pick all rebased commits instead of
 446        fast-forwarding over the unchanged ones.  This ensures that the
 447        entire history of the rebased branch is composed of new commits.
 448+
 449Without --interactive, this is a synonym for --force-rebase.
 450+
 451You may find this helpful after reverting a topic branch merge, as this option
 452recreates the topic branch with fresh commits so it can be remerged
 453successfully without needing to "revert the reversion" (see the
 454link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details).
 455
 456include::merge-strategies.txt[]
 457
 458NOTES
 459-----
 460
 461You should understand the implications of using 'git rebase' on a
 462repository that you share.  See also RECOVERING FROM UPSTREAM REBASE
 463below.
 464
 465When the git-rebase command is run, it will first execute a "pre-rebase"
 466hook if one exists.  You can use this hook to do sanity checks and
 467reject the rebase if it isn't appropriate.  Please see the template
 468pre-rebase hook script for an example.
 469
 470Upon completion, <branch> will be the current branch.
 471
 472INTERACTIVE MODE
 473----------------
 474
 475Rebasing interactively means that you have a chance to edit the commits
 476which are rebased.  You can reorder the commits, and you can
 477remove them (weeding out bad or otherwise unwanted patches).
 478
 479The interactive mode is meant for this type of workflow:
 480
 4811. have a wonderful idea
 4822. hack on the code
 4833. prepare a series for submission
 4844. submit
 485
 486where point 2. consists of several instances of
 487
 488a) regular use
 489
 490 1. finish something worthy of a commit
 491 2. commit
 492
 493b) independent fixup
 494
 495 1. realize that something does not work
 496 2. fix that
 497 3. commit it
 498
 499Sometimes the thing fixed in b.2. cannot be amended to the not-quite
 500perfect commit it fixes, because that commit is buried deeply in a
 501patch series.  That is exactly what interactive rebase is for: use it
 502after plenty of "a"s and "b"s, by rearranging and editing
 503commits, and squashing multiple commits into one.
 504
 505Start it with the last commit you want to retain as-is:
 506
 507        git rebase -i <after-this-commit>
 508
 509An editor will be fired up with all the commits in your current branch
 510(ignoring merge commits), which come after the given commit.  You can
 511reorder the commits in this list to your heart's content, and you can
 512remove them.  The list looks more or less like this:
 513
 514-------------------------------------------
 515pick deadbee The oneline of this commit
 516pick fa1afe1 The oneline of the next commit
 517...
 518-------------------------------------------
 519
 520The oneline descriptions are purely for your pleasure; 'git rebase' will
 521not look at them but at the commit names ("deadbee" and "fa1afe1" in this
 522example), so do not delete or edit the names.
 523
 524By replacing the command "pick" with the command "edit", you can tell
 525'git rebase' to stop after applying that commit, so that you can edit
 526the files and/or the commit message, amend the commit, and continue
 527rebasing.
 528
 529If you just want to edit the commit message for a commit, replace the
 530command "pick" with the command "reword".
 531
 532To drop a commit, replace the command "pick" with "drop", or just
 533delete the matching line.
 534
 535If you want to fold two or more commits into one, replace the command
 536"pick" for the second and subsequent commits with "squash" or "fixup".
 537If the commits had different authors, the folded commit will be
 538attributed to the author of the first commit.  The suggested commit
 539message for the folded commit is the concatenation of the commit
 540messages of the first commit and of those with the "squash" command,
 541but omits the commit messages of commits with the "fixup" command.
 542
 543'git rebase' will stop when "pick" has been replaced with "edit" or
 544when a command fails due to merge errors. When you are done editing
 545and/or resolving conflicts you can continue with `git rebase --continue`.
 546
 547For example, if you want to reorder the last 5 commits, such that what
 548was HEAD~4 becomes the new HEAD. To achieve that, you would call
 549'git rebase' like this:
 550
 551----------------------
 552$ git rebase -i HEAD~5
 553----------------------
 554
 555And move the first patch to the end of the list.
 556
 557You might want to preserve merges, if you have a history like this:
 558
 559------------------
 560           X
 561            \
 562         A---M---B
 563        /
 564---o---O---P---Q
 565------------------
 566
 567Suppose you want to rebase the side branch starting at "A" to "Q". Make
 568sure that the current HEAD is "B", and call
 569
 570-----------------------------
 571$ git rebase -i -p --onto Q O
 572-----------------------------
 573
 574Reordering and editing commits usually creates untested intermediate
 575steps.  You may want to check that your history editing did not break
 576anything by running a test, or at least recompiling at intermediate
 577points in history by using the "exec" command (shortcut "x").  You may
 578do so by creating a todo list like this one:
 579
 580-------------------------------------------
 581pick deadbee Implement feature XXX
 582fixup f1a5c00 Fix to feature XXX
 583exec make
 584pick c0ffeee The oneline of the next commit
 585edit deadbab The oneline of the commit after
 586exec cd subdir; make test
 587...
 588-------------------------------------------
 589
 590The interactive rebase will stop when a command fails (i.e. exits with
 591non-0 status) to give you an opportunity to fix the problem. You can
 592continue with `git rebase --continue`.
 593
 594The "exec" command launches the command in a shell (the one specified
 595in `$SHELL`, or the default shell if `$SHELL` is not set), so you can
 596use shell features (like "cd", ">", ";" ...). The command is run from
 597the root of the working tree.
 598
 599----------------------------------
 600$ git rebase -i --exec "make test"
 601----------------------------------
 602
 603This command lets you check that intermediate commits are compilable.
 604The todo list becomes like that:
 605
 606--------------------
 607pick 5928aea one
 608exec make test
 609pick 04d0fda two
 610exec make test
 611pick ba46169 three
 612exec make test
 613pick f4593f9 four
 614exec make test
 615--------------------
 616
 617SPLITTING COMMITS
 618-----------------
 619
 620In interactive mode, you can mark commits with the action "edit".  However,
 621this does not necessarily mean that 'git rebase' expects the result of this
 622edit to be exactly one commit.  Indeed, you can undo the commit, or you can
 623add other commits.  This can be used to split a commit into two:
 624
 625- Start an interactive rebase with `git rebase -i <commit>^`, where
 626  <commit> is the commit you want to split.  In fact, any commit range
 627  will do, as long as it contains that commit.
 628
 629- Mark the commit you want to split with the action "edit".
 630
 631- When it comes to editing that commit, execute `git reset HEAD^`.  The
 632  effect is that the HEAD is rewound by one, and the index follows suit.
 633  However, the working tree stays the same.
 634
 635- Now add the changes to the index that you want to have in the first
 636  commit.  You can use `git add` (possibly interactively) or
 637  'git gui' (or both) to do that.
 638
 639- Commit the now-current index with whatever commit message is appropriate
 640  now.
 641
 642- Repeat the last two steps until your working tree is clean.
 643
 644- Continue the rebase with `git rebase --continue`.
 645
 646If you are not absolutely sure that the intermediate revisions are
 647consistent (they compile, pass the testsuite, etc.) you should use
 648'git stash' to stash away the not-yet-committed changes
 649after each commit, test, and amend the commit if fixes are necessary.
 650
 651
 652RECOVERING FROM UPSTREAM REBASE
 653-------------------------------
 654
 655Rebasing (or any other form of rewriting) a branch that others have
 656based work on is a bad idea: anyone downstream of it is forced to
 657manually fix their history.  This section explains how to do the fix
 658from the downstream's point of view.  The real fix, however, would be
 659to avoid rebasing the upstream in the first place.
 660
 661To illustrate, suppose you are in a situation where someone develops a
 662'subsystem' branch, and you are working on a 'topic' that is dependent
 663on this 'subsystem'.  You might end up with a history like the
 664following:
 665
 666------------
 667    o---o---o---o---o---o---o---o  master
 668         \
 669          o---o---o---o---o  subsystem
 670                           \
 671                            *---*---*  topic
 672------------
 673
 674If 'subsystem' is rebased against 'master', the following happens:
 675
 676------------
 677    o---o---o---o---o---o---o---o  master
 678         \                       \
 679          o---o---o---o---o       o'--o'--o'--o'--o'  subsystem
 680                           \
 681                            *---*---*  topic
 682------------
 683
 684If you now continue development as usual, and eventually merge 'topic'
 685to 'subsystem', the commits from 'subsystem' will remain duplicated forever:
 686
 687------------
 688    o---o---o---o---o---o---o---o  master
 689         \                       \
 690          o---o---o---o---o       o'--o'--o'--o'--o'--M  subsystem
 691                           \                         /
 692                            *---*---*-..........-*--*  topic
 693------------
 694
 695Such duplicates are generally frowned upon because they clutter up
 696history, making it harder to follow.  To clean things up, you need to
 697transplant the commits on 'topic' to the new 'subsystem' tip, i.e.,
 698rebase 'topic'.  This becomes a ripple effect: anyone downstream from
 699'topic' is forced to rebase too, and so on!
 700
 701There are two kinds of fixes, discussed in the following subsections:
 702
 703Easy case: The changes are literally the same.::
 704
 705        This happens if the 'subsystem' rebase was a simple rebase and
 706        had no conflicts.
 707
 708Hard case: The changes are not the same.::
 709
 710        This happens if the 'subsystem' rebase had conflicts, or used
 711        `--interactive` to omit, edit, squash, or fixup commits; or
 712        if the upstream used one of `commit --amend`, `reset`, or
 713        `filter-branch`.
 714
 715
 716The easy case
 717~~~~~~~~~~~~~
 718
 719Only works if the changes (patch IDs based on the diff contents) on
 720'subsystem' are literally the same before and after the rebase
 721'subsystem' did.
 722
 723In that case, the fix is easy because 'git rebase' knows to skip
 724changes that are already present in the new upstream.  So if you say
 725(assuming you're on 'topic')
 726------------
 727    $ git rebase subsystem
 728------------
 729you will end up with the fixed history
 730------------
 731    o---o---o---o---o---o---o---o  master
 732                                 \
 733                                  o'--o'--o'--o'--o'  subsystem
 734                                                   \
 735                                                    *---*---*  topic
 736------------
 737
 738
 739The hard case
 740~~~~~~~~~~~~~
 741
 742Things get more complicated if the 'subsystem' changes do not exactly
 743correspond to the ones before the rebase.
 744
 745NOTE: While an "easy case recovery" sometimes appears to be successful
 746      even in the hard case, it may have unintended consequences.  For
 747      example, a commit that was removed via `git rebase
 748      --interactive` will be **resurrected**!
 749
 750The idea is to manually tell 'git rebase' "where the old 'subsystem'
 751ended and your 'topic' began", that is, what the old merge-base
 752between them was.  You will have to find a way to name the last commit
 753of the old 'subsystem', for example:
 754
 755* With the 'subsystem' reflog: after 'git fetch', the old tip of
 756  'subsystem' is at `subsystem@{1}`.  Subsequent fetches will
 757  increase the number.  (See linkgit:git-reflog[1].)
 758
 759* Relative to the tip of 'topic': knowing that your 'topic' has three
 760  commits, the old tip of 'subsystem' must be `topic~3`.
 761
 762You can then transplant the old `subsystem..topic` to the new tip by
 763saying (for the reflog case, and assuming you are on 'topic' already):
 764------------
 765    $ git rebase --onto subsystem subsystem@{1}
 766------------
 767
 768The ripple effect of a "hard case" recovery is especially bad:
 769'everyone' downstream from 'topic' will now have to perform a "hard
 770case" recovery too!
 771
 772BUGS
 773----
 774The todo list presented by `--preserve-merges --interactive` does not
 775represent the topology of the revision graph.  Editing commits and
 776rewording their commit messages should work fine, but attempts to
 777reorder commits tend to produce counterintuitive results.
 778
 779For example, an attempt to rearrange
 780------------
 7811 --- 2 --- 3 --- 4 --- 5
 782------------
 783to
 784------------
 7851 --- 2 --- 4 --- 3 --- 5
 786------------
 787by moving the "pick 4" line will result in the following history:
 788------------
 789        3
 790       /
 7911 --- 2 --- 4 --- 5
 792------------
 793
 794GIT
 795---
 796Part of the linkgit:git[1] suite