git-rebase - Forward-port local commits to the updated upstream head at Linux.org

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GIT-REBASE(1) Git Manual GIT-REBASE(1)

NAME
git-rebase - Forward-port local commits to the updated upstream head

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.

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. 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 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 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":

A---B---C topic
/
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:

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

will result in:

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.

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:

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:

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:

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

would result in the removal of commits F and G:

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

CONFIGURATION
rebase.stat
Whether to show a diffstat of what changed upstream since the last rebase. False by default.

rebase.autosquash
If set to true enable --autosquash option by default.

OPTIONS
--onto <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.

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.

<upstream>
Upstream branch to compare against. May be any valid commit, not just an existing branch name. Defaults to
the configured upstream for the current branch.

<branch>
Working branch; defaults to HEAD.

--continue
Restart the rebasing process after having resolved a merge conflict.

--abort
Abort the rebase operation and reset HEAD to the original branch. If <branch> was provided when the rebase
operation was started, then HEAD will be reset to <branch>. Otherwise HEAD will be reset to where it was
when the rebase operation was started.

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.

-s <strategy>, --strategy=<strategy>
Use the given merge strategy. If there is no -s option git merge-recursive is used instead. This implies
--merge.

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 discards all patches from the <branch>, which makes little
sense.

-X <strategy-option>, --strategy-option=<strategy-option>
Pass the <strategy-option> through to the merge strategy. This implies --merge and, if no strategy has
been specified, -s recursive. Note the reversal of ours and theirs as noted above for the -m option.

-q, --quiet
Be quiet. Implies --no-stat.

-v, --verbose
Be verbose. Implies --stat.

--stat
Show a diffstat of what changed upstream since the last rebase. The diffstat is also controlled by the
configuration option rebase.stat.

-n, --no-stat
Do not show a diffstat as part of the rebase process.

--no-verify
This option bypasses the pre-rebase hook. See also githooks(5).

--verify
Allows the pre-rebase hook to run, which is the default. This option can be used to override --no-verify.
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.

-f, --force-rebase
Force the rebase even if the current branch is a descendant of the commit you are rebasing onto. Normally
non-interactive rebase will exit with the message "Current branch is up to date" in such a situation.
Incompatible with the --interactive option.

You may find this (or --no-ff with an interactive rebase) 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).

--ignore-whitespace, --whitespace=<option>
These flag are passed to the git apply program (see git-apply(1)) that applies the patch. Incompatible
with the --interactive option.

explicitly is generally not a good idea unless you know what you are doing (see BUGS below).

-x <cmd>, --exec <cmd>
Append "exec <cmd>" after each line creating a commit in the final history. <cmd> will be interpreted as
one or more shell commands.

This option can only be used with the --interactive option (see INTERACTIVE MODE below).

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.

--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. When used with --onto, it will skip changes already contained in
<newbase> (instead of <upstream>) whereas without --onto it will operate on every change. When used
together with both --onto and --preserve-merges, all root commits will be rewritten to have <newbase> as
parent instead.

--autosquash, --no-autosquash
When the commit log message begins with "squash! ..." (or "fixup! ..."), and there is a commit whose title
begins with the same ..., automatically modify the todo list of rebase -i so that the commit marked for
squashing comes right after the commit to be modified, and change the action of the moved commit from pick
to squash (or fixup).

This option is only valid when the --interactive option is used.

If the --autosquash option is enabled by default using the configuration variable rebase.autosquash, this
option can be used to override and disable this setting.

--no-ff
With --interactive, cherry-pick all rebased commits instead of fast-forwarding over the unchanged ones.
This ensures that the entire history of the rebased branch is composed of new commits.

Without --interactive, this is a synonym for --force-rebase.

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).

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.

resolve
This can only resolve two heads (i.e. the current branch and another branch you pulled from) using a 3-way

ours
This option forces conflicting hunks to be auto-resolved cleanly by favoring our version. Changes from
the other tree that do not conflict with our side are reflected to the merge result. For a binary
file, the entire contents are taken from our side.

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
This is the opposite of ours.

patience
With this option, merge-recursive spends a little extra time to avoid mismerges that sometimes occur
due to unimportant matching lines (e.g., braces from distinct functions). Use this when the branches
to be merged have diverged wildly. See also git-diff(1)--patience.

diff-algorithm=[patience|minimal|histogram|myers]
Tells merge-recursive to use a different diff algorithm, which can help avoid mismerges that occur due
to unimportant matching lines (such as braces from distinct functions). See also git-
diff(1)--diff-algorithm.

ignore-space-change, ignore-all-space, ignore-space-at-eol
Treats lines with the indicated type of whitespace change as unchanged for the sake of a three-way
merge. Whitespace changes mixed with other changes to a line are not ignored. See also git-diff(1)-b,
-w, and --ignore-space-at-eol.

· If their version only introduces whitespace changes to a line, our version is used;

· If our version introduces whitespace changes but their version includes a substantial change,
their version is used;

· Otherwise, the merge proceeds in the usual way.

renormalize
This runs a virtual check-out and check-in of all three stages of a file when resolving a three-way
merge. This option is meant to be used when merging branches with different clean filters or
end-of-line normalization rules. See "Merging branches with differing checkin/checkout attributes" in
gitattributes(5) for details.

no-renormalize
Disables the renormalize option. This overrides the merge.renormalize configuration variable.

rename-threshold=<n>
Controls the similarity threshold used for rename detection. See also git-diff(1)-M.

subtree[=<path>]
This option is a more advanced form of subtree strategy, where the strategy makes a guess on how two
trees must be shifted to match with each other when merging. Instead, the specified path is prefixed
(or stripped from the beginning) to make the shape of two trees to match.

octopus
This resolves cases with more than two heads, but refuses to do a complex merge that needs manual
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

where point 2. consists of several instances of

a) regular use

1. finish something worthy of a commit

2. commit

b) independent fixup

1. realize that something does not work

2. fix that

3. commit it

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:

"reword".

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 commit messages of the first commit and of those with the "squash" command, but omits the commit messages
of commits with the "fixup" command.

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 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

$ git rebase -i -p --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 one specified in $SHELL, or the default shell if
$SHELL is not set), so you can use shell features (like "cd", ">", ";" ...). The command is run from the root
of the working tree.

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:

· 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.

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:

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:

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

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, squash, or fixup
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!

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:

· 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.

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):

$ 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
to

1 --- 2 --- 4 --- 3 --- 5

by moving the "pick 4" line will result in the following history:

3
/
1 --- 2 --- 4 --- 5

GIT
Part of the git(1) suite

NOTES
1. revert-a-faulty-merge How-To
file:///usr/share/doc/git-1.8.3.1/howto/revert-a-faulty-merge.txt

Git 1.8.3.1 03/23/2016 GIT-REBASE(1)