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diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt new file mode 100644 index 000000000..c8ad86a56 --- /dev/null +++ b/Documentation/git-rebase.txt @@ -0,0 +1,532 @@ +git-rebase(1) +============= + +NAME +---- +git-rebase - Forward-port local commits to the updated upstream head + +SYNOPSIS +-------- +[verse] +'git rebase' [-i | --interactive] [-v | --verbose] [-m | --merge] + [-s <strategy> | --strategy=<strategy>] [--no-verify] + [-C<n>] [ --whitespace=<option>] [-p | --preserve-merges] + [--onto <newbase>] <upstream> [<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`. + +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: + + + git rebase master + git rebase master topic + +would be: + +------------ + 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: + +------------ + 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 +------------ + +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 + + git rebase --onto topicA~5 topicA~3 topicA + +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 + +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 linkgit: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=<nowarn|warn|error|error-all|strip>:: + This flag is passed to the 'git-apply' program + (see linkgit:git-apply[1]) that applies the patch. + +-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. + +include::merge-strategies.txt[] + +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: + +------------------------------------------- +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 + +----------------------------- +$ 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`. + +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' 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**! + +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 linkgit: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 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 +--- +Part of the linkgit:git[1] suite |