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git-rebase
Langue: en
Version: 04/04/2009 (fedora - 04/07/09)
Section: 1 (Commandes utilisateur)
Sommaire
NAME
git-rebase - Forward-port local commits to the updated upstream headSYNOPSIS
git rebase [-i | --interactive] [options] [--onto <newbase>]
<upstream> [<branch>]
git rebase [-i | --interactive] [options] --onto <newbase>
--root [<branch>]
git rebase --continue | --skip | --abort
DESCRIPTION
If <branch> is specified, git-rebase will perform an automatic git checkout <branch> before doing anything else. Otherwise it remains on the current branch.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 git log HEAD, if --root 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.
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 restore 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":
-
A---B---C topic / D---E---F---G master
From this point, the result of either of the following commands:
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git rebase master git rebase master topic
would be:
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A'--B'--C' topic / D---E---F---G master
The latter form is just a short-hand of git checkout topic followed by git rebase master.
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. 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):
-
A---B---C topic / D---E---A'---F master
will result in:
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B'---C' topic / 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.
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o---o---o---o---o master \ o---o---o---o---o next \ 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:
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o---o---o---o---o master | \ | o'--o'--o' topic \ 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:
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H---I---J topicB / E---F---G topicA / A---B---C---D master
then the command
-
git rebase --onto master topicA topicB
would result in:
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H'--I'--J' topicB / | E---F---G topicA |/ 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:
-
E---F---G---H---I---J topicA
then the command
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git rebase --onto topicA~5 topicA~3 topicA
would result in the removal of commits F and G:
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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
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git add <filename>
After resolving the conflict manually and updating the index with the desired resolution, you can continue the rebasing process with
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git rebase --continue
Alternatively, you can undo the git-rebase with
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git rebase --abort
OPTIONS
<newbase>
- Starting point at which to create the new commits. If the --onto option is not specified, the starting point is <upstream>. May be any valid commit, and not just an existing branch name.
<upstream>
- Upstream branch to compare against. May be any valid commit, not just an existing branch name.
<branch>
- Working branch; defaults to HEAD.
--continue
- Restart the rebasing process after having resolved a merge conflict.
--abort
- Restore the original branch and abort the rebase operation.
--skip
- Restart the rebasing process by skipping the current patch.
-m, --merge
- Use merging strategies to rebase. When the recursive (default) merge strategy is used, this allows rebase to be aware of renames on the upstream side.
-s <strategy>, --strategy=<strategy>
- Use the given merge strategy; can be supplied more than once to specify them in the order they should be tried. If there is no -s option, a built-in list of strategies is used instead (git-merge-recursive when merging a single head, git-merge-octopus otherwise). This implies --merge.
-v, --verbose
- Display a diffstat of what changed upstream since the last rebase.
--no-verify
- This option bypasses the pre-rebase hook. See also githooks(5).
-C<n>
- Ensure at least <n> lines of surrounding context match before and after each change. When fewer lines of surrounding context exist they all must match. By default no context is ever ignored.
--whitespace=<option>
- This flag is passed to the git-apply program (see git-apply(1)) that applies the patch. Incompatible with the --interactive option.
-i, --interactive
- Make a list of the commits which are about to be rebased. Let the user edit that list before rebasing. This mode can also be used to split commits (see SPLITTING COMMITS below).
-p, --preserve-merges
- Instead of ignoring merges, try to recreate them.
--root
- Rebase all commits reachable from <branch>, instead of limiting them with an <upstream>. This allows you to rebase the root commit(s) on a branch. Must be used with --onto, and will skip changes already contained in <newbase> (instead of <upstream>). When used together with --preserve-merges, all root commits will be rewritten to have <newbase> as parent instead.
MERGE STRATEGIES
resolve
- This can only resolve two heads (i.e. the current branch and another branch you pulled from) using 3-way merge algorithm. It tries to carefully detect criss-cross merge ambiguities and is considered generally safe and fast.
recursive
- This can only resolve two heads using 3-way merge algorithm. When there are more than one common ancestors that can be used for 3-way merge, it creates a merged tree of the common ancestors and uses that as the reference tree for the 3-way merge. This has been reported to result in fewer merge conflicts without causing mis-merges by tests done on actual merge commits taken from Linux 2.6 kernel development history. Additionally this can detect and handle merges involving renames. This is the default merge strategy when pulling or merging one branch.
octopus
- This resolves more than two-head case, but refuses to do complex merge that needs manual resolution. It is primarily meant to be used for bundling topic branch heads together. This is the default merge strategy when pulling or merging more than one branches.
ours
- This resolves any number of heads, but the result of the merge is always the current branch head. It is meant to be used to supersede old development history of side branches.
subtree
- This is a modified recursive strategy. When merging trees A and B, if B corresponds to a subtree of A, B is first adjusted to match the tree structure of A, instead of reading the trees at the same level. This adjustment is also done to the common ancestor tree.
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 git-rebase command 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:
- 1. have a wonderful idea
- 2. hack on the code
- 3. prepare a series for submission
- 4. submit
- 1. regular use
-
- 1. finish something worthy of a commit
- 2. commit
- 2. independent fixup
-
- 1. realize that something does not work
- 2. fix that
- 3. commit it
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.
If you want to fold two or more commits into one, replace the command "pick" with "squash" for the second and subsequent commit. If the commits had different authors, it will attribute the squashed commit to the author of the first commit.
In both cases, or when a "pick" does not succeed (because of merge errors), the loop will stop to let you fix things, and you can continue the loop 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 preserve merges, if you have a history like this:
-
X \ A---M---B / ---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
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$ git rebase -i -p --onto Q O
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:- • Start an interactive rebase with git rebase -i <commit>^, where <commit> is the commit you want to split. In fact, any commit range will do, as long as it contains that commit.
- • Mark the commit you want to split with the action "edit".
- • When it comes to editing that commit, execute git reset HEAD^. The effect is that the HEAD is rewound by one, and the index follows suit. However, the working tree stays the same.
- • Now add the changes to the index that you want to have in the first commit. You can use git add (possibly interactively) or git-gui (or both) to do that.
- • Commit the now-current index with whatever commit message is appropriate now.
- • Repeat the last two steps until your working tree is clean.
- • Continue the rebase with git rebase --continue.
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:
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o---o---o---o---o---o---o---o---o master \ o---o---o---o---o subsystem \ *---*---* topic
If subsystem is rebased against master, the following happens:
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o---o---o---o---o---o---o---o master \ \ o---o---o---o---o o'--o'--o'--o'--o' subsystem \ *---*---* topic
If you now continue development as usual, and eventually merge topic to subsystem, the commits from subsystem will remain duplicated forever:
-
o---o---o---o---o---o---o---o master \ \ o---o---o---o---o o'--o'--o'--o'--o'--M subsystem \ / *---*---*-..........-*--* 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.
- This happens if the subsystem rebase was a simple rebase and had no conflicts.
Hard case: The changes are not the same.
- This happens if the subsystem rebase had conflicts, or used --interactive to omit, edit, or squash commits; or if the upstream used one of commit --amend, reset, or filter-branch.
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. So if you say (assuming you're on topic)
-
$ git rebase subsystem
you will end up with the fixed history
-
o---o---o---o---o---o---o---o master \ o'--o'--o'--o'--o' subsystem \ *---*---* topic
The hard case
Things get more complicated if the subsystem changes do not exactly correspond to the ones before the rebase.
Note
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!
- • With the subsystem reflog: after git-fetch, the old tip of subsystem is at subsystem@{1}. Subsequent fetches will increase the number. (See git-reflog(1).)
- • Relative to the tip of topic: knowing that your topic has three commits, the old tip of subsystem must be topic~3.
-
$ 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!
AUTHORS
Written by Junio C Hamano <gitster@pobox.com> and Johannes E. Schindelin <johannes.schindelin@gmx.de>DOCUMENTATION
Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.GIT
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