git-rebase(1)

NAME#

git-rebase - Reapply commits on top of another base tip

SYNOPSIS#

git rebase\n [-i | --interactive] [<options>] [--exec <cmd>]
\n
        [--onto <newbase> | --keep-base] [<upstream> [<branch>]]
\ngit rebase\n [-i | --interactive] [<options>] [--exec <cmd>] [--onto <newbase>]
\n
        --root [<branch>]
\ngit rebase\n (--continue|--skip|--abort|--quit|--edit-todo|--show-current-patch)

DESCRIPTION#

If <branch> is specified, git rebase will perform an automatic git switch <branch> before doing anything else. Otherwise it remains on the current branch.

If <upstream> is not specified, the upstream configured in branch.<name>.remote and branch.<name>.merge options will be used (see git-config(1) for details) and the --fork-point option is assumed. If you are currently not on any branch or if the current branch does not have a configured upstream, the rebase will abort.

All changes made by commits in the current branch but that are not in <upstream> are saved to a temporary area. This is the same set of commits that would be shown by git log <upstream>..HEAD; or by git log 'fork_point'..HEAD, if --fork-point is active (see the description on --fork-point below); or by git log HEAD, if the --root option is specified.

The current branch is reset to <upstream> or <newbase> if the --onto option was supplied. This has the exact same effect as git reset --hard <upstream> (or <newbase>). ORIG_HEAD is set to point at the tip of the branch before the reset.

ORIG_HEAD is not guaranteed to still point to the previous branch tip at the end of the rebase if other commands that write that pseudo-ref (e.g. git reset) are used during the rebase. The previous branch tip, however, is accessible using the reflog of the current branch (i.e. @{1}, see gitrevisions(7)).

The commits that were previously saved into the temporary area are then reapplied to the current branch, one by one, in order. Note that any commits in HEAD which introduce the same textual changes as a commit in HEAD..<upstream> are omitted (i.e., a patch already accepted upstream with a different commit message or timestamp will be skipped).

It is possible that a merge failure will prevent this process from being completely automatic. You will have to resolve any such merge failure and run git rebase --continue. Another option is to bypass the commit that caused the merge failure with git rebase --skip. To check out the original <branch> and remove the .git/rebase-apply working files, use the command git rebase --abort instead.

Assume the following history exists and the current branch is "topic":

\n
          A---B---C topic
\n
         /
\n
    D---E---F---G master

From this point, the result of either of the following commands:

git rebase master
git rebase master topic

would be:

\n
                  A'--B'--C' topic
\n
                 /
\n
    D---E---F---G master

NOTE: The latter form is just a short-hand of git checkout topic followed by git rebase master. When rebase exits topic will remain the checked-out branch.

If the upstream branch already contains a change you have made (e.g., because you mailed a patch which was applied upstream), then that commit will be skipped and warnings will be issued (if the merge backend is used). For example, running git rebase master on the following history (in which A' and A introduce the same set of changes, but have different committer information):

\n
          A---B---C topic
\n
         /
\n
    D---E---A'---F master

will result in:

\n
                   B'---C' topic
\n
                  /
\n
    D---E---A'---F master

Here is how you would transplant a topic branch based on one branch to another, to pretend that you forked the topic branch from the latter branch, using rebase --onto.

First let’s assume your topic is based on branch next. For example, a feature developed in topic depends on some functionality which is found in next.

\n
    o---o---o---o---o  master
\n
         \
\n
          o---o---o---o---o  next
\n
                           \
\n
                            o---o---o  topic

We want to make topic forked from branch master; for example, because the functionality on which topic depends was merged into the more stable master branch. We want our tree to look like this:

\n
    o---o---o---o---o  master
\n
        |            \
\n
        |             o'--o'--o'  topic
\n
         \
\n
          o---o---o---o---o  next

We can get this using the following command:

git rebase --onto master next topic

Another example of --onto option is to rebase part of a branch. If we have the following situation:

\n
                            H---I---J topicB
\n
                           /
\n
                  E---F---G  topicA
\n
                 /
\n
    A---B---C---D  master

then the command

git rebase --onto master topicA topicB

would result in:

\n
                 H'--I'--J'  topicB
\n
                /
\n
                | E---F---G  topicA
\n
                |/
\n
    A---B---C---D  master

This is useful when topicB does not depend on topicA.

A range of commits could also be removed with rebase. If we have the following situation:

\n
    E---F---G---H---I---J  topicA

then the command

git rebase --onto topicA~5 topicA~3 topicA

would result in the removal of commits F and G:

\n
    E---H'---I'---J'  topicA

This is useful if F and G were flawed in some way, or should not be part of topicA. Note that the argument to --onto and the <upstream> parameter can be any valid commit-ish.

In case of conflict, git rebase will stop at the first problematic commit and leave conflict markers in the tree. You can use git diff to locate the markers (<<<<<<) and make edits to resolve the conflict. For each file you edit, you need to tell Git that the conflict has been resolved, typically this would be done with

git add <filename>

After resolving the conflict manually and updating the index with the desired resolution, you can continue the rebasing process with

git rebase --continue

Alternatively, you can undo the git rebase with

git rebase --abort

MODE OPTIONS#

The options in this section cannot be used with any other option, including not with each other:

--continue

--skip

--abort

--quit

--edit-todo

--show-current-patch

OPTIONS#

--onto <newbase>

As a special case, you may use "A...B" as a shortcut for the merge base of A and B if there is exactly one merge base. You can leave out at most one of A and B, in which case it defaults to HEAD.

--keep-base

This option is useful in the case where one is developing a feature on top of an upstream branch. While the feature is being worked on, the upstream branch may advance and it may not be the best idea to keep rebasing on top of the upstream but to keep the base commit as-is. As the base commit is unchanged this option implies --reapply-cherry-picks to avoid losing commits.

Although both this option and --fork-point find the merge base between <upstream> and <branch>, this option uses the merge base as the starting point on which new commits will be created, whereas --fork-point uses the merge base to determine the set of commits which will be rebased.

See also INCOMPATIBLE OPTIONS below.

<upstream>

<branch>

--apply

See also INCOMPATIBLE OPTIONS below.

--empty=(drop|keep|stop)

drop

keep

stop, ask

Note that commits which start empty are kept (unless --no-keep-empty is specified), and commits which are clean cherry-picks (as determined by git log --cherry-mark ...) are detected and dropped as a preliminary step (unless --reapply-cherry-picks or --keep-base is passed).

See also INCOMPATIBLE OPTIONS below.

--no-keep-empty, --keep-empty

Usage of this flag will probably be rare, since you can get rid of commits that start empty by just firing up an interactive rebase and removing the lines corresponding to the commits you don’t want. This flag exists as a convenient shortcut, such as for cases where external tools generate many empty commits and you want them all removed.

For commits which do not start empty but become empty after rebasing, see the --empty flag.

See also INCOMPATIBLE OPTIONS below.

--reapply-cherry-picks, --no-reapply-cherry-picks

In the absence of --keep-base (or if --no-reapply-cherry-picks is given), these commits will be automatically dropped. Because this necessitates reading all upstream commits, this can be expensive in repositories with a large number of upstream commits that need to be read. When using the merge backend, warnings will be issued for each dropped commit (unless --quiet is given). Advice will also be issued unless advice.skippedCherryPicks is set to false (see git-config(1)).

--reapply-cherry-picks allows rebase to forgo reading all upstream commits, potentially improving performance.

See also INCOMPATIBLE OPTIONS below.

--allow-empty-message

See also INCOMPATIBLE OPTIONS below.

-m, --merge

Note that a rebase merge works by replaying each commit from the working branch on top of the <upstream> branch. Because of this, when a merge conflict happens, the side reported as ours is the so-far rebased series, starting with <upstream>, and theirs is the working branch. In other words, the sides are swapped.

See also INCOMPATIBLE OPTIONS below.

-s <strategy>, --strategy=<strategy>

Because git rebase replays each commit from the working branch on top of the <upstream> branch using the given strategy, using the ours strategy simply empties all patches from the <branch>, which makes little sense.

See also INCOMPATIBLE OPTIONS below.

-X <strategy-option>, --strategy-option=<strategy-option>

See also INCOMPATIBLE OPTIONS below.

--rerere-autoupdate, --no-rerere-autoupdate

-S[<keyid>], --gpg-sign[=<keyid>], --no-gpg-sign

-q, --quiet

-v, --verbose

--stat

-n, --no-stat

--no-verify

--verify

-C<n>

See also INCOMPATIBLE OPTIONS below.

--no-ff, --force-rebase, -f

You may find this helpful after reverting a topic branch merge, as this option recreates the topic branch with fresh commits so it can be remerged successfully without needing to "revert the reversion" (see the revert-a-faulty-merge How-To[1] for details).

--fork-point, --no-fork-point

When --fork-point is active, fork_point will be used instead of <upstream> to calculate the set of commits to rebase, where fork_point is the result of git merge-base --fork-point <upstream> <branch> command (see git-merge-base(1)). If fork_point ends up being empty, the <upstream> will be used as a fallback.

If <upstream> or --keep-base is given on the command line, then the default is --no-fork-point, otherwise the default is --fork-point. See also rebase.forkpoint in git-config(1).

If your branch was based on <upstream> but <upstream> was rewound and your branch contains commits which were dropped, this option can be used with --keep-base in order to drop those commits from your branch.

See also INCOMPATIBLE OPTIONS below.

--ignore-whitespace

apply backend

merge backend

--whitespace=<option>

See also INCOMPATIBLE OPTIONS below.

--committer-date-is-author-date

--ignore-date, --reset-author-date

See also INCOMPATIBLE OPTIONS below.

--signoff

See also INCOMPATIBLE OPTIONS below.

-i, --interactive

The commit list format can be changed by setting the configuration option rebase.instructionFormat. A customized instruction format will automatically have the commit hash prepended to the format.

See also INCOMPATIBLE OPTIONS below.

-r, --rebase-merges[=(rebase-cousins|no-rebase-cousins)], --no-rebase-merges

When rebasing merges, there are two modes: rebase-cousins and no-rebase-cousins. If the mode is not specified, it defaults to no-rebase-cousins. In no-rebase-cousins mode, commits which do not have <upstream> as direct ancestor will keep their original branch point, i.e. commits that would be excluded by git-log(1)'s --ancestry-path option will keep their original ancestry by default. In rebase-cousins mode, such commits are instead rebased onto <upstream> (or <onto>, if specified).

It is currently only possible to recreate the merge commits using the ort merge strategy; different merge strategies can be used only via explicit exec git merge -s <strategy> [...] commands.

See also REBASING MERGES and INCOMPATIBLE OPTIONS below.

-x <cmd>, --exec <cmd>

You may execute several commands by either using one instance of --exec with several commands:

git rebase -i --exec "cmd1 && cmd2 && ..."

or by giving more than one --exec:

git rebase -i --exec "cmd1" --exec "cmd2" --exec ...

If --autosquash is used, exec lines will not be appended for the intermediate commits, and will only appear at the end of each squash/fixup series.

This uses the --interactive machinery internally, but it can be run without an explicit --interactive.

See also INCOMPATIBLE OPTIONS below.

--root

See also INCOMPATIBLE OPTIONS below.

--autosquash, --no-autosquash

In the rebase todo list, the actions of squash, fixup and amend commits are changed from pick to squash, fixup or fixup -C, respectively, and they are moved right after the commit they modify. The --interactive option can be used to review and edit the todo list before proceeding.

The recommended way to create commits with squash markers is by using the --squash, --fixup, --fixup=amend: or --fixup=reword: options of git-commit(1), which take the target commit as an argument and automatically fill in the subject line of the new commit from that.

Setting configuration variable rebase.autoSquash to true enables auto-squashing by default for interactive rebase. The --no-autosquash option can be used to override that setting.

See also INCOMPATIBLE OPTIONS below.

--autostash, --no-autostash

--reschedule-failed-exec, --no-reschedule-failed-exec

This option applies once a rebase is started. It is preserved for the whole rebase based on, in order, the command line option provided to the initial git rebase, the rebase.rescheduleFailedExec configuration (see git-config(1) or "CONFIGURATION" below), or it defaults to false.

Recording this option for the whole rebase is a convenience feature. Otherwise an explicit --no-reschedule-failed-exec at the start would be overridden by the presence of a rebase.rescheduleFailedExec=true configuration when git rebase --continue is invoked. Currently, you cannot pass --[no-]reschedule-failed-exec to git rebase --continue.

--update-refs, --no-update-refs

If the configuration variable rebase.updateRefs is set, then this option can be used to override and disable this setting.

See also INCOMPATIBLE OPTIONS below.

INCOMPATIBLE OPTIONS#

The following options:

are incompatible with the following options:

In addition, the following pairs of options are incompatible:

BEHAVIORAL DIFFERENCES#

git rebase has two primary backends: apply and merge. (The apply backend used to be known as the am backend, but the name led to confusion as it looks like a verb instead of a noun. Also, the merge backend used to be known as the interactive backend, but it is now used for non-interactive cases as well. Both were renamed based on lower-level functionality that underpinned each.) There are some subtle differences in how these two backends behave:

Empty commits#

The apply backend unfortunately drops intentionally empty commits, i.e. commits that started empty, though these are rare in practice. It also drops commits that become empty and has no option for controlling this behavior.

The merge backend keeps intentionally empty commits by default (though with -i they are marked as empty in the todo list editor, or they can be dropped automatically with --no-keep-empty).

Similar to the apply backend, by default the merge backend drops commits that become empty unless -i/--interactive is specified (in which case it stops and asks the user what to do). The merge backend also has an --empty=(drop|keep|stop) option for changing the behavior of handling commits that become empty.

Directory rename detection#

Due to the lack of accurate tree information (arising from constructing fake ancestors with the limited information available in patches), directory rename detection is disabled in the apply backend. Disabled directory rename detection means that if one side of history renames a directory and the other adds new files to the old directory, then the new files will be left behind in the old directory without any warning at the time of rebasing that you may want to move these files into the new directory.

Directory rename detection works with the merge backend to provide you warnings in such cases.

Context#

The apply backend works by creating a sequence of patches (by calling format-patch internally), and then applying the patches in sequence (calling am internally). Patches are composed of multiple hunks, each with line numbers, a context region, and the actual changes. The line numbers have to be taken with some offset, since the other side will likely have inserted or deleted lines earlier in the file. The context region is meant to help find how to adjust the line numbers in order to apply the changes to the right lines. However, if multiple areas of the code have the same surrounding lines of context, the wrong one can be picked. There are real-world cases where this has caused commits to be reapplied incorrectly with no conflicts reported. Setting diff.context to a larger value may prevent such types of problems, but increases the chance of spurious conflicts (since it will require more lines of matching context to apply).

The merge backend works with a full copy of each relevant file, insulating it from these types of problems.

Labelling of conflicts markers#

When there are content conflicts, the merge machinery tries to annotate each side’s conflict markers with the commits where the content came from. Since the apply backend drops the original information about the rebased commits and their parents (and instead generates new fake commits based off limited information in the generated patches), those commits cannot be identified; instead it has to fall back to a commit summary. Also, when merge.conflictStyle is set to diff3 or zdiff3, the apply backend will use "constructed merge base" to label the content from the merge base, and thus provide no information about the merge base commit whatsoever.

The merge backend works with the full commits on both sides of history and thus has no such limitations.

Hooks#

The apply backend has not traditionally called the post-commit hook, while the merge backend has. Both have called the post-checkout hook, though the merge backend has squelched its output. Further, both backends only call the post-checkout hook with the starting point commit of the rebase, not the intermediate commits nor the final commit. In each case, the calling of these hooks was by accident of implementation rather than by design (both backends were originally implemented as shell scripts and happened to invoke other commands like git checkout or git commit that would call the hooks). Both backends should have the same behavior, though it is not entirely clear which, if any, is correct. We will likely make rebase stop calling either of these hooks in the future.

Interruptability#

The apply backend has safety problems with an ill-timed interrupt; if the user presses Ctrl-C at the wrong time to try to abort the rebase, the rebase can enter a state where it cannot be aborted with a subsequent git rebase --abort. The merge backend does not appear to suffer from the same shortcoming. (See https://lore.kernel.org/git/[email protected]/ for details.)

Commit Rewording#

When a conflict occurs while rebasing, rebase stops and asks the user to resolve. Since the user may need to make notable changes while resolving conflicts, after conflicts are resolved and the user has run git rebase --continue, the rebase should open an editor and ask the user to update the commit message. The merge backend does this, while the apply backend blindly applies the original commit message.

Miscellaneous differences#

There are a few more behavioral differences that most folks would probably consider inconsequential but which are mentioned for completeness:

MERGE STRATEGIES#

The merge mechanism (git merge and git pull commands) allows the backend merge strategies to be chosen with -s option. Some strategies can also take their own options, which can be passed by giving -X<option> arguments to git merge and/or git pull.

ort

The ort strategy can take the following options:

ours

This should not be confused with the ours merge strategy, which does not even look at what the other tree contains at all. It discards everything the other tree did, declaring our history contains all that happened in it.

theirs

ignore-space-change, ignore-all-space, ignore-space-at-eol, ignore-cr-at-eol

renormalize

no-renormalize

find-renames[=<n>]

rename-threshold=<n>

subtree[=<path>]

recursive

The recursive strategy takes the same options as ort. However, there are three additional options that ort ignores (not documented above) that are potentially useful with the recursive strategy:

patience

diff-algorithm=[patience|minimal|histogram|myers]

no-renames

resolve

octopus

ours

subtree

With the strategies that use 3-way merge (including the default, ort), if a change is made on both branches, but later reverted on one of the branches, that change will be present in the merged result; some people find this behavior confusing. It occurs because only the heads and the merge base are considered when performing a merge, not the individual commits. The merge algorithm therefore considers the reverted change as no change at all, and substitutes the changed version instead.

NOTES#

You should understand the implications of using git rebase on a repository that you share. See also RECOVERING FROM UPSTREAM REBASE below.

When the rebase is run, it will first execute a pre-rebase hook if one exists. You can use this hook to do sanity checks and reject the rebase if it isn’t appropriate. Please see the template pre-rebase hook script for an example.

Upon completion, <branch> will be the current branch.

INTERACTIVE MODE#

Rebasing interactively means that you have a chance to edit the commits which are rebased. You can reorder the commits, and you can remove them (weeding out bad or otherwise unwanted patches).

The interactive mode is meant for this type of workflow:

where point 2. consists of several instances of

a) regular use

b) independent fixup

Sometimes the thing fixed in b.2. cannot be amended to the not-quite perfect commit it fixes, because that commit is buried deeply in a patch series. That is exactly what interactive rebase is for: use it after plenty of "a"s and "b"s, by rearranging and editing commits, and squashing multiple commits into one.

Start it with the last commit you want to retain as-is:

git rebase -i <after-this-commit>

An editor will be fired up with all the commits in your current branch (ignoring merge commits), which come after the given commit. You can reorder the commits in this list to your heart’s content, and you can remove them. The list looks more or less like this:

pick deadbee The oneline of this commit
pick fa1afe1 The oneline of the next commit
...

The oneline descriptions are purely for your pleasure; git rebase will not look at them but at the commit names ("deadbee" and "fa1afe1" in this example), so do not delete or edit the names.

By replacing the command "pick" with the command "edit", you can tell git rebase to stop after applying that commit, so that you can edit the files and/or the commit message, amend the commit, and continue rebasing.

To interrupt the rebase (just like an "edit" command would do, but without cherry-picking any commit first), use the "break" command.

If you just want to edit the commit message for a commit, replace the command "pick" with the command "reword".

To drop a commit, replace the command "pick" with "drop", or just delete the matching line.

If you want to fold two or more commits into one, replace the command "pick" for the second and subsequent commits with "squash" or "fixup". If the commits had different authors, the folded commit will be attributed to the author of the first commit. The suggested commit message for the folded commit is the concatenation of the first commit’s message with those identified by "squash" commands, omitting the messages of commits identified by "fixup" commands, unless "fixup -c" is used. In that case the suggested commit message is only the message of the "fixup -c" commit, and an editor is opened allowing you to edit the message. The contents (patch) of the "fixup -c" commit are still incorporated into the folded commit. If there is more than one "fixup -c" commit, the message from the final one is used. You can also use "fixup -C" to get the same behavior as "fixup -c" except without opening an editor.

git rebase will stop when "pick" has been replaced with "edit" or when a command fails due to merge errors. When you are done editing and/or resolving conflicts you can continue with git rebase --continue.

For example, if you want to reorder the last 5 commits, such that what was HEAD~4 becomes the new HEAD. To achieve that, you would call git rebase like this:

$ git rebase -i HEAD~5

And move the first patch to the end of the list.

You might want to recreate merge commits, e.g. if you have a history like this:

\n
           X
\n
            \
\n
         A---M---B
\n
        /
---o---O---P---Q

Suppose you want to rebase the side branch starting at "A" to "Q". Make sure that the current HEAD is "B", and call

$ git rebase -i -r --onto Q O

Reordering and editing commits usually creates untested intermediate steps. You may want to check that your history editing did not break anything by running a test, or at least recompiling at intermediate points in history by using the "exec" command (shortcut "x"). You may do so by creating a todo list like this one:

pick deadbee Implement feature XXX
fixup f1a5c00 Fix to feature XXX
exec make
pick c0ffeee The oneline of the next commit
edit deadbab The oneline of the commit after
exec cd subdir; make test
...

The interactive rebase will stop when a command fails (i.e. exits with non-0 status) to give you an opportunity to fix the problem. You can continue with git rebase --continue.

The "exec" command launches the command in a shell (the default one, usually /bin/sh), so you can use shell features (like "cd", ">", ";" ...). The command is run from the root of the working tree.

$ git rebase -i --exec "make test"

This command lets you check that intermediate commits are compilable. The todo list becomes like that:

pick 5928aea one
exec make test
pick 04d0fda two
exec make test
pick ba46169 three
exec make test
pick f4593f9 four
exec make test

SPLITTING COMMITS#

In interactive mode, you can mark commits with the action "edit". However, this does not necessarily mean that git rebase expects the result of this edit to be exactly one commit. Indeed, you can undo the commit, or you can add other commits. This can be used to split a commit into two:

If you are not absolutely sure that the intermediate revisions are consistent (they compile, pass the testsuite, etc.) you should use git stash to stash away the not-yet-committed changes after each commit, test, and amend the commit if fixes are necessary.

RECOVERING FROM UPSTREAM REBASE#

Rebasing (or any other form of rewriting) a branch that others have based work on is a bad idea: anyone downstream of it is forced to manually fix their history. This section explains how to do the fix from the downstream’s point of view. The real fix, however, would be to avoid rebasing the upstream in the first place.

To illustrate, suppose you are in a situation where someone develops a subsystem branch, and you are working on a topic that is dependent on this subsystem. You might end up with a history like the following:

\n
    o---o---o---o---o---o---o---o  master
\n
         \
\n
          o---o---o---o---o  subsystem
\n
                           \
\n
                            *---*---*  topic

If subsystem is rebased against master, the following happens:

\n
    o---o---o---o---o---o---o---o  master
\n
         \                       \
\n
          o---o---o---o---o       o'--o'--o'--o'--o'  subsystem
\n
                           \
\n
                            *---*---*  topic

If you now continue development as usual, and eventually merge topic to subsystem, the commits from subsystem will remain duplicated forever:

\n
    o---o---o---o---o---o---o---o  master
\n
         \                       \
\n
          o---o---o---o---o       o'--o'--o'--o'--o'--M  subsystem
\n
                           \                         /
\n
                            *---*---*-..........-*--*  topic

Such duplicates are generally frowned upon because they clutter up history, making it harder to follow. To clean things up, you need to transplant the commits on topic to the new subsystem tip, i.e., rebase topic. This becomes a ripple effect: anyone downstream from topic is forced to rebase too, and so on!

There are two kinds of fixes, discussed in the following subsections:

Easy case: The changes are literally the same.

Hard case: The changes are not the same.

The easy case#

Only works if the changes (patch IDs based on the diff contents) on subsystem are literally the same before and after the rebase subsystem did.

In that case, the fix is easy because git rebase knows to skip changes that are already present in the new upstream (unless --reapply-cherry-picks is given). So if you say (assuming you’re on topic)

\n
    $ git rebase subsystem

you will end up with the fixed history

\n
    o---o---o---o---o---o---o---o  master
\n
                                 \
\n
                                  o'--o'--o'--o'--o'  subsystem
\n
                                                   \
\n
                                                    *---*---*  topic

The hard case#

Things get more complicated if the subsystem changes do not exactly correspond to the ones before the rebase.

While an "easy case recovery" sometimes appears to be successful even in the hard case, it may have unintended consequences. For example, a commit that was removed via git rebase --interactive will be resurrected!

The idea is to manually tell git rebase "where the old subsystem ended and your topic began", that is, what the old merge base between them was. You will have to find a way to name the last commit of the old subsystem, for example:

You can then transplant the old subsystem..topic to the new tip by saying (for the reflog case, and assuming you are on topic already):

\n
    $ git rebase --onto subsystem subsystem@{1}

The ripple effect of a "hard case" recovery is especially bad: everyone downstream from topic will now have to perform a "hard case" recovery too!

REBASING MERGES#

The interactive rebase command was originally designed to handle individual patch series. As such, it makes sense to exclude merge commits from the todo list, as the developer may have merged the then-current master while working on the branch, only to rebase all the commits onto master eventually (skipping the merge commits).

However, there are legitimate reasons why a developer may want to recreate merge commits: to keep the branch structure (or "commit topology") when working on multiple, inter-related branches.

In the following example, the developer works on a topic branch that refactors the way buttons are defined, and on another topic branch that uses that refactoring to implement a "Report a bug" button. The output of git log --graph --format=%s -5 may look like this:

*   Merge branch 'report-a-bug'
|\
| * Add the feedback button
* | Merge branch 'refactor-button'
|\ \
| |/
| * Use the Button class for all buttons
| * Extract a generic Button class from the DownloadButton one

The developer might want to rebase those commits to a newer master while keeping the branch topology, for example when the first topic branch is expected to be integrated into master much earlier than the second one, say, to resolve merge conflicts with changes to the DownloadButton class that made it into master.

This rebase can be performed using the --rebase-merges option. It will generate a todo list looking like this:

label onto
# Branch: refactor-button
reset onto
pick 123456 Extract a generic Button class from the DownloadButton one
pick 654321 Use the Button class for all buttons
label refactor-button
# Branch: report-a-bug
reset refactor-button # Use the Button class for all buttons
pick abcdef Add the feedback button
label report-a-bug
reset onto
merge -C a1b2c3 refactor-button # Merge 'refactor-button'
merge -C 6f5e4d report-a-bug # Merge 'report-a-bug'

In contrast to a regular interactive rebase, there are label, reset and merge commands in addition to pick ones.

The label command associates a label with the current HEAD when that command is executed. These labels are created as worktree-local refs (refs/rewritten/<label>) that will be deleted when the rebase finishes. That way, rebase operations in multiple worktrees linked to the same repository do not interfere with one another. If the label command fails, it is rescheduled immediately, with a helpful message how to proceed.

The reset command resets the HEAD, index and worktree to the specified revision. It is similar to an exec git reset --hard <label>, but refuses to overwrite untracked files. If the reset command fails, it is rescheduled immediately, with a helpful message how to edit the todo list (this typically happens when a reset command was inserted into the todo list manually and contains a typo).

The merge command will merge the specified revision(s) into whatever is HEAD at that time. With -C <original-commit>, the commit message of the specified merge commit will be used. When the -C is changed to a lower-case -c, the message will be opened in an editor after a successful merge so that the user can edit the message.

If a merge command fails for any reason other than merge conflicts (i.e. when the merge operation did not even start), it is rescheduled immediately.

By default, the merge command will use the ort merge strategy for regular merges, and octopus for octopus merges. One can specify a default strategy for all merges using the --strategy argument when invoking rebase, or can override specific merges in the interactive list of commands by using an exec command to call git merge explicitly with a --strategy argument. Note that when calling git merge explicitly like this, you can make use of the fact that the labels are worktree-local refs (the ref refs/rewritten/onto would correspond to the label onto, for example) in order to refer to the branches you want to merge.

Note: the first command (label onto) labels the revision onto which the commits are rebased; The name onto is just a convention, as a nod to the --onto option.

It is also possible to introduce completely new merge commits from scratch by adding a command of the form merge <merge-head>. This form will generate a tentative commit message and always open an editor to let the user edit it. This can be useful e.g. when a topic branch turns out to address more than a single concern and wants to be split into two or even more topic branches. Consider this todo list:

pick 192837 Switch from GNU Makefiles to CMake
pick 5a6c7e Document the switch to CMake
pick 918273 Fix detection of OpenSSL in CMake
pick afbecd http: add support for TLS v1.3
pick fdbaec Fix detection of cURL in CMake on Windows

The one commit in this list that is not related to CMake may very well have been motivated by working on fixing all those bugs introduced by switching to CMake, but it addresses a different concern. To split this branch into two topic branches, the todo list could be edited like this:

label onto
pick afbecd http: add support for TLS v1.3
label tlsv1.3
reset onto
pick 192837 Switch from GNU Makefiles to CMake
pick 918273 Fix detection of OpenSSL in CMake
pick fdbaec Fix detection of cURL in CMake on Windows
pick 5a6c7e Document the switch to CMake
label cmake
reset onto
merge tlsv1.3
merge cmake

CONFIGURATION#

Everything below this line in this section is selectively included from the git-config(1) documentation. The content is the same as what’s found there:

rebase.backend

rebase.stat

rebase.autoSquash

rebase.autoStash

rebase.updateRefs

rebase.missingCommitsCheck

rebase.instructionFormat

rebase.abbreviateCommands

\n
        p deadbee The oneline of the commit
\n
        p fa1afe1 The oneline of the next commit
\n
        ...

instead of:

\n
        pick deadbee The oneline of the commit
\n
        pick fa1afe1 The oneline of the next commit
\n
        ...

Defaults to false.

rebase.rescheduleFailedExec

rebase.forkPoint

rebase.rebaseMerges

rebase.maxLabelLength

sequence.editor

GIT#

Part of the git(1) suite

NOTES#

1.

revert-a-faulty-merge How-To

2.

filter-repo