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| -rw-r--r-- | Documentation/git-rerere.txt | 177 | ||||
| -rw-r--r-- | Documentation/git.txt | 3 | ||||
| -rw-r--r-- | Makefile | 2 | ||||
| -rwxr-xr-x | git-am.sh | 1 | ||||
| -rwxr-xr-x | git-commit.sh | 1 | ||||
| -rwxr-xr-x | git-merge.sh | 1 | ||||
| -rwxr-xr-x | git-rerere.perl | 223 | ||||
| -rwxr-xr-x | git-reset.sh | 2 |
8 files changed, 408 insertions, 2 deletions
diff --git a/Documentation/git-rerere.txt b/Documentation/git-rerere.txt new file mode 100644 index 0000000..8b6b651 --- /dev/null +++ b/Documentation/git-rerere.txt @@ -0,0 +1,177 @@ +git-rerere(1) +============= + +NAME +---- +git-rerere - Reuse recorded resolve + +SYNOPSIS +-------- +'git-rerere' + + +DESCRIPTION +----------- + +In a workflow that employs relatively long lived topic branches, +the developer sometimes needs to resolve the same conflict over +and over again until the topic branches are done (either merged +to the "release" branch, or sent out and accepted upstream). + +This command helps this process by recording conflicted +automerge results and corresponding hand-resolve results on the +initial manual merge, and later by noticing the same automerge +results and applying the previously recorded hand resolution. + +[NOTE] +You need to create `$GIT_DIR/rr-cache` directory to enable this +command. + +DISCUSSION +---------- + +When your topic branch modifies overlapping area that your +master branch (or upstream) touched since your topic branch +forked from it, you may want to test it with the latest master, +even before your topic branch is ready to be pushed upstream: + +------------ + o---*---o topic + / + o---o---o---*---o---o master +------------ + +For such a test, you need to merge master and topic somehow. +One way to do it is to pull master into the topic branch: + +------------ + $ git checkout topic + $ git pull . master + + o---*---o---+ topic + / / + o---o---o---*---o---o master +------------ + +The commits marked with `*` touch the same area in the same +file; you need to resolve the conflicts when creating the commit +marked with `+`. Then you can test the result to make sure your +work-in-progress still works with what is in the latest master. + +After this test merge, there are two ways to continue your work +on the topic. The easiest is to build on top of the test merge +commit `+`, and when your work in the topic branch is finally +ready, pull the topic branch into master, and/or ask the +upstream to pull from you. By that time, however, the master or +the upstream might have been advanced since the test merge `+`, +in which case the final commit graph would look like this: + +------------ + $ git checkout topic + $ git pull . master + $ ... work on both topic and master branches + $ git checkout master + $ git pull . topic + + o---*---o---+---o---o topic + / / \ + o---o---o---*---o---o---o---o---+ master +------------ + +When your topic branch is long-lived, however, your topic branch +would end up having many such "Merge from master" commits on it, +which would unnecessarily clutter the development history. +Readers of the Linux kernel mailing list may remember that Linus +complained about such too frequent test merges when a subsystem +maintainer asked to pull from a branch full of "useless merges". + +As an alternative, to keep the topic branch clean of test +merges, you could blow away the test merge, and keep building on +top of the tip before the test merge: + +------------ + $ git checkout topic + $ git pull . master + $ git reset --hard HEAD^ ;# rewind the test merge + $ ... work on both topic and master branches + $ git checkout master + $ git pull . topic + + o---*---o-------o---o topic + / \ + o---o---o---*---o---o---o---o---+ master +------------ + +This would leave only one merge commit when your topic branch is +finally ready and merged into the master branch. This merge +would require you to resolve the conflict, introduced by the +commits marked with `*`. However, often this conflict is the +same conflict you resolved when you created the test merge you +blew away. `git-rerere` command helps you to resolve this final +conflicted merge using the information from your earlier hand +resolve. + +Running `git-rerere` command immediately after a conflicted +automerge records the conflicted working tree files, with the +usual conflict markers `<<<<<<<`, `=======`, and `>>>>>>>` in +them. Later, after you are done resolving the conflicts, +running `git-rerere` again records the resolved state of these +files. Suppose you did this when you created the test merge of +master into the topic branch. + +Next time, running `git-rerere` after seeing a conflicted +automerge, if the conflict is the same as the earlier one +recorded, it is noticed and a three-way merge between the +earlier conflicted automerge, the earlier manual resolution, and +the current conflicted automerge is performed by the command. +If this three-way merge resolves cleanly, the result is written +out to your working tree file, so you would not have to manually +resolve it. Note that `git-rerere` leaves the index file alone, +so you still need to do the final sanity checks with `git diff` +(or `git diff -c`) and `git update-index` when you are +satisfied. + +As a convenience measure, `git-merge` automatically invokes +`git-rerere` when it exits with a failed automerge, which +records it if it is a new conflict, or reuses the earlier hand +resolve when it is not. `git-commit` also invokes `git-rerere` +when recording a merge result. What this means is that you do +not have to do anything special yourself (Note: you still have +to create `$GIT_DIR/rr-cache` directory to enable this command). + +In our example, when you did the test merge, the manual +resolution is recorded, and it will be reused when you do the +actual merge later with updated master and topic branch, as long +as the earlier resolution is still applicable. + +The information `git-rerere` records is also used when running +`git-rebase`. After blowing away the test merge and continuing +development on the topic branch: + +------------ + o---*---o-------o---o topic + / + o---o---o---*---o---o---o---o master + + $ git rebase master topic + + o---*---o-------o---o topic + / + o---o---o---*---o---o---o---o master +------------ + +you could run `git rebase master topic`, to keep yourself +up-to-date even before your topic is ready to be sent upstream. +This would result in falling back to three-way merge, and it +would conflict the same way the test merge you resolved earlier. +`git-rerere` is run by `git rebase` to help you resolve this +conflict. + + +Author +------ +Written by Junio C Hamano <junkio@cox.net> + +GIT +--- +Part of the gitlink:git[7] suite diff --git a/Documentation/git.txt b/Documentation/git.txt index e8ef3efa..2d0ca9d 100644 --- a/Documentation/git.txt +++ b/Documentation/git.txt @@ -313,6 +313,9 @@ gitlink:git-rebase[1]:: gitlink:git-repack[1]:: Pack unpacked objects in a repository. +gitlink:git-rerere[1]:: + Reuse recorded resolution of conflicted merges. + gitlink:git-reset[1]:: Reset current HEAD to the specified state. @@ -116,7 +116,7 @@ SCRIPT_SH = \ SCRIPT_PERL = \ git-archimport.perl git-cvsimport.perl git-relink.perl \ - git-shortlog.perl git-fmt-merge-msg.perl \ + git-shortlog.perl git-fmt-merge-msg.perl git-rerere.perl \ git-svnimport.perl git-mv.perl git-cvsexportcommit.perl SCRIPT_PYTHON = \ @@ -88,6 +88,7 @@ fall_back_3way () { # saying that we reverted all those changes. git-merge-resolve $orig_tree -- HEAD $his_tree || { + git-rerere echo Failed to merge in the changes. exit 1 } diff --git a/git-commit.sh b/git-commit.sh index 10946ed..9c94083 100755 --- a/git-commit.sh +++ b/git-commit.sh @@ -245,6 +245,7 @@ else fi ret="$?" rm -f "$GIT_DIR/COMMIT_MSG" "$GIT_DIR/COMMIT_EDITMSG" +git-rerere if test -x "$GIT_DIR"/hooks/post-commit && test "$ret" = 0 then diff --git a/git-merge.sh b/git-merge.sh index 8c0a92c..dc17baf 100755 --- a/git-merge.sh +++ b/git-merge.sh @@ -309,5 +309,6 @@ Conflicts: sed -e 's/^[^ ]* / /' | uniq } >>"$GIT_DIR/MERGE_MSG" + git rerere die "Automatic merge failed; fix up by hand" fi diff --git a/git-rerere.perl b/git-rerere.perl new file mode 100755 index 0000000..df11951 --- /dev/null +++ b/git-rerere.perl @@ -0,0 +1,223 @@ +#!/usr/bin/perl +# +# REuse REcorded REsolve. This tool records a conflicted automerge +# result and its hand resolution, and helps to resolve future +# automerge that results in the same conflict. +# +# To enable this feature, create a directory 'rr-cache' under your +# .git/ directory. + +use Digest; +use File::Path; +use File::Copy; + +my $git_dir = $::ENV{GIT_DIR} || ".git"; +my $rr_dir = "$git_dir/rr-cache"; +my $merge_rr = "$git_dir/rr-cache/MERGE_RR"; + +my %merge_rr = (); + +sub read_rr { + if (!-f $merge_rr) { + %merge_rr = (); + return; + } + my $in; + local $/ = "\0"; + open $in, "<$merge_rr" or die "$!: $merge_rr"; + while (<$in>) { + chomp; + my ($name, $path) = /^([0-9a-f]{40})\t(.*)$/s; + $merge_rr{$path} = $name; + } + close $in; +} + +sub write_rr { + my $out; + open $out, ">$merge_rr" or die "$!: $merge_rr"; + for my $path (sort keys %merge_rr) { + my $name = $merge_rr{$path}; + print $out "$name\t$path\0"; + } + close $out; +} + +sub compute_conflict_name { + my ($path) = @_; + my @side = (); + my $in; + open $in, "<$path" or die "$!: $path"; + + my $sha1 = Digest->new("SHA-1"); + my $hunk = 0; + while (<$in>) { + if (/^<<<<<<< .*/) { + $hunk++; + @side = ([], undef); + } + elsif (/^=======$/) { + $side[1] = []; + } + elsif (/^>>>>>>> .*/) { + my ($one, $two); + $one = join('', @{$side[0]}); + $two = join('', @{$side[1]}); + if ($two le $one) { + ($one, $two) = ($two, $one); + } + $sha1->add($one); + $sha1->add("\0"); + $sha1->add($two); + $sha1->add("\0"); + @side = (); + } + elsif (@side == 0) { + next; + } + elsif (defined $side[1]) { + push @{$side[1]}, $_; + } + else { + push @{$side[0]}, $_; + } + } + close $in; + return ($sha1->hexdigest, $hunk); +} + +sub record_preimage { + my ($path, $name) = @_; + my @side = (); + my ($in, $out); + open $in, "<$path" or die "$!: $path"; + open $out, ">$name" or die "$!: $name"; + + while (<$in>) { + if (/^<<<<<<< .*/) { + @side = ([], undef); + } + elsif (/^=======$/) { + $side[1] = []; + } + elsif (/^>>>>>>> .*/) { + my ($one, $two); + $one = join('', @{$side[0]}); + $two = join('', @{$side[1]}); + if ($two le $one) { + ($one, $two) = ($two, $one); + } + print $out "<<<<<<<\n"; + print $out $one; + print $out "=======\n"; + print $out $two; + print $out ">>>>>>>\n"; + @side = (); + } + elsif (@side == 0) { + print $out $_; + } + elsif (defined $side[1]) { + push @{$side[1]}, $_; + } + else { + push @{$side[0]}, $_; + } + } + close $out; + close $in; +} + +sub find_conflict { + my $in; + local $/ = "\0"; + open $in, '-|', qw(git ls-files -z -u) or die "$!: ls-files"; + my %path = (); + my @path = (); + while (<$in>) { + chomp; + my ($mode, $sha1, $stage, $path) = + /^([0-7]+) ([0-9a-f]{40}) ([123])\t(.*)$/s; + $path{$path} |= (1 << $stage); + } + close $in; + while (my ($path, $status) = each %path) { + if ($status == 14) { push @path, $path; } + } + return @path; +} + +sub merge { + my ($name, $path) = @_; + record_preimage($path, "$rr_dir/$name/thisimage"); + unless (system('merge', map { "$rr_dir/$name/${_}image" } + qw(this pre post))) { + my $in; + open $in, "<$rr_dir/$name/thisimage" or + die "$!: $name/thisimage"; + my $out; + open $out, ">$path" or die "$!: $path"; + while (<$in>) { print $out $_; } + close $in; + close $out; + return 1; + } + return 0; +} + +-d "$rr_dir" || exit(0); + +read_rr(); +my %conflict = map { $_ => 1 } find_conflict(); + +# MERGE_RR records paths with conflicts immediately after merge +# failed. Some of the conflicted paths might have been hand resolved +# in the working tree since then, but the initial run would catch all +# and register their preimages. + +for my $path (keys %conflict) { + # This path has conflict. If it is not recorded yet, + # record the pre-image. + if (!exists $merge_rr{$path}) { + my ($name, $hunk) = compute_conflict_name($path); + next unless ($hunk); + $merge_rr{$path} = $name; + if (! -d "$rr_dir/$name") { + mkpath("$rr_dir/$name", 0, 0777); + print STDERR "Recorded preimage for '$path'\n"; + record_preimage($path, "$rr_dir/$name/preimage"); + } + } +} + +# Now some of the paths that had conflicts earlier might have been +# hand resolved. Others may be similar to a conflict already that +# was resolved before. + +for my $path (keys %merge_rr) { + my $name = $merge_rr{$path}; + + # We could resolve this automatically if we have images. + if (-f "$rr_dir/$name/preimage" && + -f "$rr_dir/$name/postimage") { + if (merge($name, $path)) { + print STDERR "Resolved '$path' using previous resolution.\n"; + # Then we do not have to worry about this path + # anymore. + delete $merge_rr{$path}; + next; + } + } + + # Let's see if we have resolved it. + (undef, my $hunk) = compute_conflict_name($path); + next if ($hunk); + + print STDERR "Recorded resolution for '$path'.\n"; + copy($path, "$rr_dir/$name/postimage"); + # And we do not have to worry about this path anymore. + delete $merge_rr{$path}; +} + +# Write out the rest. +write_rr(); diff --git a/git-reset.sh b/git-reset.sh index 6c9e58a..fe53fc8 100755 --- a/git-reset.sh +++ b/git-reset.sh @@ -100,4 +100,4 @@ case "$reset_type" in ;; esac -rm -f "$GIT_DIR/MERGE_HEAD" +rm -f "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/rr-cache/MERGE_RR" |