diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/git-rebase.txt | 135 | ||||
| -rw-r--r-- | Documentation/technical/directory-rename-detection.txt | 115 |
2 files changed, 223 insertions, 27 deletions
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt index 091eb53faa..a7850415b1 100644 --- a/Documentation/git-rebase.txt +++ b/Documentation/git-rebase.txt @@ -243,11 +243,15 @@ leave out at most one of A and B, in which case it defaults to HEAD. --keep-empty:: Keep the commits that do not change anything from its parents in the result. ++ +See also INCOMPATIBLE OPTIONS below. --allow-empty-message:: By default, rebasing commits with an empty message will fail. This option overrides that behavior, allowing commits with empty messages to be rebased. ++ +See also INCOMPATIBLE OPTIONS below. --skip:: Restart the rebasing process by skipping the current patch. @@ -271,6 +275,8 @@ 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>:: @@ -280,8 +286,10 @@ other words, the sides are swapped. + 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>, +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>:: @@ -289,6 +297,8 @@ which makes little sense. 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. ++ +See also INCOMPATIBLE OPTIONS below. -S[<keyid>]:: --gpg-sign[=<keyid>]:: @@ -324,17 +334,21 @@ which makes little sense. and after each change. When fewer lines of surrounding context exist they all must match. By default no context is ever ignored. ++ +See also INCOMPATIBLE OPTIONS below. --f:: +--no-ff:: --force-rebase:: - Force a rebase even if the current branch is up to date and - the command without `--force` would return without doing anything. +-f:: + Individually replay 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. + -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 -link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details). +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 +link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for +details). --fork-point:: --no-fork-point:: @@ -355,19 +369,22 @@ default is `--no-fork-point`, otherwise the default is `--fork-point`. --whitespace=<option>:: These flag are passed to the 'git apply' program (see linkgit:git-apply[1]) that applies the patch. - Incompatible with the --interactive option. ++ +See also INCOMPATIBLE OPTIONS below. --committer-date-is-author-date:: --ignore-date:: These flags are passed to 'git am' to easily change the dates of the rebased commits (see linkgit:git-am[1]). - Incompatible with the --interactive option. ++ +See also INCOMPATIBLE OPTIONS below. --signoff:: Add a Signed-off-by: trailer to all the rebased commits. Note that if `--interactive` is given then only commits marked to be - picked, edited or reworded will have the trailer added. Incompatible - with the `--preserve-merges` option. + picked, edited or reworded will have the trailer added. ++ +See also INCOMPATIBLE OPTIONS below. -i:: --interactive:: @@ -378,6 +395,8 @@ default is `--no-fork-point`, otherwise the default is `--fork-point`. The commit list format can be changed by setting the configuration option rebase.instructionFormat. A customized instruction format will automatically have the long commit hash prepended to the format. ++ +See also INCOMPATIBLE OPTIONS below. -r:: --rebase-merges[=(rebase-cousins|no-rebase-cousins)]:: @@ -404,7 +423,7 @@ It is currently only possible to recreate the merge commits using the `recursive` merge strategy; Different merge strategies can be used only via explicit `exec git merge -s <strategy> [...]` commands. + -See also REBASING MERGES below. +See also REBASING MERGES and INCOMPATIBLE OPTIONS below. -p:: --preserve-merges:: @@ -415,6 +434,8 @@ See also REBASING MERGES below. This uses the `--interactive` machinery internally, but combining it with the `--interactive` option explicitly is generally not a good idea unless you know what you are doing (see BUGS below). ++ +See also INCOMPATIBLE OPTIONS below. -x <cmd>:: --exec <cmd>:: @@ -437,6 +458,8 @@ squash/fixup series. + This uses the `--interactive` machinery internally, but it can be run without an explicit `--interactive`. ++ +See also INCOMPATIBLE OPTIONS below. --root:: Rebase all commits reachable from <branch>, instead of @@ -447,6 +470,8 @@ without an explicit `--interactive`. When used together with both --onto and --preserve-merges, 'all' root commits will be rewritten to have <newbase> as parent instead. ++ +See also INCOMPATIBLE OPTIONS below. --autosquash:: --no-autosquash:: @@ -461,11 +486,11 @@ without an explicit `--interactive`. too. The recommended way to create fixup/squash commits is by using the `--fixup`/`--squash` options of linkgit:git-commit[1]. + -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. ++ +See also INCOMPATIBLE OPTIONS below. --autostash:: --no-autostash:: @@ -475,17 +500,73 @@ used to override and disable this setting. with care: the final stash application after a successful rebase might result in non-trivial conflicts. ---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 -link:howto/revert-a-faulty-merge.html[revert-a-faulty-merge How-To] for details). +INCOMPATIBLE OPTIONS +-------------------- + +git-rebase has many flags that are incompatible with each other, +predominantly due to the fact that it has three different underlying +implementations: + + * one based on linkgit:git-am[1] (the default) + * one based on git-merge-recursive (merge backend) + * one based on linkgit:git-cherry-pick[1] (interactive backend) + +Flags only understood by the am backend: + + * --committer-date-is-author-date + * --ignore-date + * --whitespace + * --ignore-whitespace + * -C + +Flags understood by both merge and interactive backends: + + * --merge + * --strategy + * --strategy-option + * --allow-empty-message + +Flags only understood by the interactive backend: + + * --[no-]autosquash + * --rebase-merges + * --preserve-merges + * --interactive + * --exec + * --keep-empty + * --autosquash + * --edit-todo + * --root when used in combination with --onto + +Other incompatible flag pairs: + + * --preserve-merges and --interactive + * --preserve-merges and --signoff + * --preserve-merges and --rebase-merges + * --rebase-merges and --strategy + * --rebase-merges and --strategy-option + +BEHAVIORAL DIFFERENCES +----------------------- + + * empty commits: + + am-based rebase will drop any "empty" commits, whether the + commit started empty (had no changes relative to its parent to + start with) or ended empty (all changes were already applied + upstream in other commits). + + merge-based rebase does the same. + + interactive-based rebase will by default drop commits that + started empty and halt if it hits a commit that ended up empty. + The `--keep-empty` option exists for interactive rebases to allow + it to keep commits that started empty. + + * directory rename detection: + + merge-based and interactive-based rebases work fine with + directory rename detection. am-based rebases sometimes do not. include::merge-strategies.txt[] diff --git a/Documentation/technical/directory-rename-detection.txt b/Documentation/technical/directory-rename-detection.txt new file mode 100644 index 0000000000..1c0086e287 --- /dev/null +++ b/Documentation/technical/directory-rename-detection.txt @@ -0,0 +1,115 @@ +Directory rename detection +========================== + +Rename detection logic in diffcore-rename that checks for renames of +individual files is aggregated and analyzed in merge-recursive for cases +where combinations of renames indicate that a full directory has been +renamed. + +Scope of abilities +------------------ + +It is perhaps easiest to start with an example: + + * When all of x/a, x/b and x/c have moved to z/a, z/b and z/c, it is + likely that x/d added in the meantime would also want to move to z/d by + taking the hint that the entire directory 'x' moved to 'z'. + +More interesting possibilities exist, though, such as: + + * one side of history renames x -> z, and the other renames some file to + x/e, causing the need for the merge to do a transitive rename. + + * one side of history renames x -> z, but also renames all files within + x. For example, x/a -> z/alpha, x/b -> z/bravo, etc. + + * both 'x' and 'y' being merged into a single directory 'z', with a + directory rename being detected for both x->z and y->z. + + * not all files in a directory being renamed to the same location; + i.e. perhaps most the files in 'x' are now found under 'z', but a few + are found under 'w'. + + * a directory being renamed, which also contained a subdirectory that was + renamed to some entirely different location. (And perhaps the inner + directory itself contained inner directories that were renamed to yet + other locations). + + * combinations of the above; see t/t6043-merge-rename-directories.sh for + various interesting cases. + +Limitations -- applicability of directory renames +------------------------------------------------- + +In order to prevent edge and corner cases resulting in either conflicts +that cannot be represented in the index or which might be too complex for +users to try to understand and resolve, a couple basic rules limit when +directory rename detection applies: + + 1) If a given directory still exists on both sides of a merge, we do + not consider it to have been renamed. + + 2) If a subset of to-be-renamed files have a file or directory in the + way (or would be in the way of each other), "turn off" the directory + rename for those specific sub-paths and report the conflict to the + user. + + 3) If the other side of history did a directory rename to a path that + your side of history renamed away, then ignore that particular + rename from the other side of history for any implicit directory + renames (but warn the user). + +Limitations -- detailed rules and testcases +------------------------------------------- + +t/t6043-merge-rename-directories.sh contains extensive tests and commentary +which generate and explore the rules listed above. It also lists a few +additional rules: + + a) If renames split a directory into two or more others, the directory + with the most renames, "wins". + + b) Avoid directory-rename-detection for a path, if that path is the + source of a rename on either side of a merge. + + c) Only apply implicit directory renames to directories if the other side + of history is the one doing the renaming. + +Limitations -- support in different commands +-------------------------------------------- + +Directory rename detection is supported by 'merge' and 'cherry-pick'. +Other git commands which users might be surprised to see limited or no +directory rename detection support in: + + * diff + + Folks have requested in the past that `git diff` detect directory + renames and somehow simplify its output. It is not clear whether this + would be desirable or how the output should be simplified, so this was + simply not implemented. Further, to implement this, directory rename + detection logic would need to move from merge-recursive to + diffcore-rename. + + * am + + git-am tries to avoid a full three way merge, instead calling + git-apply. That prevents us from detecting renames at all, which may + defeat the directory rename detection. There is a fallback, though; if + the initial git-apply fails and the user has specified the -3 option, + git-am will fall back to a three way merge. However, git-am lacks the + necessary information to do a "real" three way merge. Instead, it has + to use build_fake_ancestor() to get a merge base that is missing files + whose rename may have been important to detect for directory rename + detection to function. + + * rebase + + Since am-based rebases work by first generating a bunch of patches + (which no longer record what the original commits were and thus don't + have the necessary info from which we can find a real merge-base), and + then calling git-am, this implies that am-based rebases will not always + successfully detect directory renames either (see the 'am' section + above). merged-based rebases (rebase -m) and cherry-pick-based rebases + (rebase -i) are not affected by this shortcoming, and fully support + directory rename detection. |