Subject: [PATCH v2] git-svn: teach git-svn to populate svn:mergeinfo

From: Bryan Jacobs <[email-masked]>
Date: Wed, 7 Sep 2011 13:36:05 -0400

Allow git-svn to populate the svn:mergeinfo property automatically in
a narrow range of circumstances. Specifically, when dcommitting a
revision with multiple parents, all but (potentially) the first of
which have been committed to SVN in the same repository as the target
of the dcommit.

In this case, the merge info is the union of that given by each of the
parents, plus all changes introduced to the first parent by the other
parents.

In all other cases where a revision to be committed has multiple
parents, cause "git svn dcommit" to raise an error rather than
completing the commit and potentially losing history information in
the upstream SVN repository.

This behavior is disabled by default, and can be enabled by setting
the svn.pushmergeinfo config option.

Signed-off-by: Bryan Jacobs <[email-masked]>
---

This is the second revision of a patch I posted earlier. I believe this patch is now suitable for inclusion.

Significant changes from the last revision are:

- All revisions in the commit list are checked beforehand to ensure that all non-first-parents of merge commits have suitable SVN metadata attached.
- Cases where a merge commit is at the top of an uncommitted stack are tested and now work correctly.
- Cleanups as suggested by Eric Wong.

This code is still vulnerable to race conditions if the git repository is modified while a dcommit is in progress, but this is a fundamental problem with git-svn's continual-rebasing-series approach, as previously discussed.

I believe I have determined the source of the added+untracked files in the working copy. With this repository:

branch1: A - B
            /
branch2:   C

If a file is added in C, and you attempt to dcommit B (C must be dcommitted or the problem will be detected and the commit will abort), git-svn runs a reset --mixed. So because the files added in C were present in B, they remain present but are untracked when you reset --mixed to A. So you cannot apply B to the rebased state because it would "create" the file you already have (with, admittedly, identical contents).

I'm not clear on why git will not allow this to proceed - the file in the working copy is identical to the file that would be "created", so there's no loss of data. "file would be overwritten", yes, technically, but never altered, so no problem really... Might be a user-interface consistency issue to allow it, but I'd be inclined to say git's behavior should change.

Regardless, this could be solved by using a reset --hard to A before beginning. Since we already disallow dcommitting with a dirty WC, this should be safe (never thought I'd say that about a reset --hard). I'm not going to write that change, though.

Of course, users could also recover from even the worst disaster via the reflog.

 Documentation/git-svn.txt         |    8 +
 git-svn.perl                      |  255 +++++++++++++++++++++++++
 t/t9160-git-svn-mergeinfo-push.sh |  104 ++++++++++
 t/t9160/branches.dump             |  374 +++++++++++++++++++++++++++++++++++++
 4 files changed, 741 insertions(+), 0 deletions(-)
 create mode 100755 t/t9160-git-svn-mergeinfo-push.sh
 create mode 100644 t/t9160/branches.dump

diff --git a/Documentation/git-svn.txt b/Documentation/git-svn.txt
index ed5eca1..89955a2 100644
--- a/Documentation/git-svn.txt
+++ b/Documentation/git-svn.txt
@@ -213,6 +213,14 @@ discouraged.
 	store this information (as a property), and svn clients starting from
 	version 1.5 can make use of it. 'git svn' currently does not use it
 	and does not set it automatically.
++
+[verse]
+config key: svn.pushmergeinfo
++
+This option will cause git-svn to attempt to automatically populate the
+svn:mergeinfo property in the SVN repository when possible. Currently, this can
+only be done when dcommitting non-fast-forward merges where all parents but the
+first have already been pushed into SVN.
 
 'branch'::
 	Create a branch in the SVN repository.
diff --git a/git-svn.perl b/git-svn.perl
index 89f83fd..bf60300 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -497,6 +497,195 @@ sub cmd_set_tree {
 	unlink $gs->{index};
 }
 
+sub split_merge_info_range {
+	my ($range) = @_;
+	if ($range =~ /(\d+)-(\d+)/) {
+		return (int($1), int($2));
+	} else {
+		return (int($range), int($range));
+	}
+}
+
+sub combine_ranges {
+	my ($in) = @_;
+
+	my @fnums = ();
+	my @arr = split(/,/, $in);
+	for my $element (@arr) {
+		my ($start, $end) = split_merge_info_range($element);
+		push @fnums, $start;
+	}
+
+	my @sorted = @arr [ sort {
+		$fnums[$a] <=> $fnums[$b]
+	} 0..$#arr ];
+
+	my @return = ();
+	my $last = -1;
+	my $first = -1;
+	for my $element (@sorted) {
+		my ($start, $end) = split_merge_info_range($element);
+
+		if ($last == -1) {
+			$first = $start;
+			$last = $end;
+			next;
+		}
+		if ($start <= $last+1) {
+			if ($end > $last) {
+				$last = $end;
+			}
+			next;
+		}
+		if ($first == $last) {
+			push @return, "$first";
+		} else {
+			push @return, "$first-$last";
+		}
+		$first = $start;
+		$last = $end;
+	}
+
+	if ($first != -1) {
+		if ($first == $last) {
+			push @return, "$first";
+		} else {
+			push @return, "$first-$last";
+		}
+	}
+
+	return join(',', @return);
+}
+
+sub merge_revs_into_hash {
+	my ($hash, $minfo) = @_;
+	my @lines = split(' ', $minfo);
+
+	for my $line (@lines) {
+		my ($branchpath, $revs) = split(/:/, $line);
+
+		if (exists($hash->{$branchpath})) {
+			# Merge the two revision sets
+			my $combined = "$hash->{$branchpath},$revs";
+			$hash->{$branchpath} = combine_ranges($combined);
+		} else {
+			# Just do range combining for consolidation
+			$hash->{$branchpath} = combine_ranges($revs);
+		}
+	}
+}
+
+sub merge_merge_info {
+	my ($mergeinfo_one, $mergeinfo_two) = @_;
+	my %result_hash = ();
+
+	merge_revs_into_hash(\%result_hash, $mergeinfo_one);
+	merge_revs_into_hash(\%result_hash, $mergeinfo_two);
+
+	my $result = '';
+	# Sort below is for consistency's sake
+	for my $branchname (sort keys(%result_hash)) {
+		my $revlist = $result_hash{$branchname};
+		$result .= "$branchname:$revlist\n"
+	}
+	return $result;
+}
+
+sub populate_merge_info {
+	my ($d, $gs, $uuid, $linear_refs, $rewritten_parent) = @_;
+
+	my %parentshash;
+	read_commit_parents(\%parentshash, $d);
+	my @parents = @{$parentshash{$d}};
+	if ($#parents > 0) {
+		# Merge commit
+		my $all_parents_ok = 1;
+		my $aggregate_mergeinfo = '';
+		my $rooturl = $gs->repos_root;
+
+		if (defined($rewritten_parent)) {
+			# Replace first parent with newly-rewritten version
+			shift @parents;
+			unshift @parents, $rewritten_parent;
+		}
+
+		foreach my $parent (@parents) {
+			my ($branchurl, $svnrev, $paruuid) =
+				cmt_metadata($parent);
+
+			unless (defined($svnrev)) {
+				# Should have been caught be preflight check
+				fatal "merge commit $d has ancestor $parent, but that change "
+                     ."does not have git-svn metadata!";
+			}
+			unless ($branchurl =~ /^$rooturl(.*)/) {
+				fatal "commit $parent git-svn metadata changed mid-run!";
+			}
+			my $branchpath = $1;
+
+			my $ra = Git::SVN::Ra->new($branchurl);
+			my (undef, undef, $props) =
+				$ra->get_dir(canonicalize_path("."), $svnrev);
+			my $par_mergeinfo = $props->{'svn:mergeinfo'};
+			unless (defined $par_mergeinfo) {
+				$par_mergeinfo = '';
+			}
+			# Merge previous mergeinfo values
+			$aggregate_mergeinfo =
+				merge_merge_info($aggregate_mergeinfo,
+								 $par_mergeinfo, 0);
+
+			next if $parent eq $parents[0]; # Skip first parent
+			# Add new changes being placed in tree by merge
+			my @cmd = (qw/rev-list --reverse/,
+					   $parent, qw/--not/);
+			foreach my $par (@parents) {
+				unless ($par eq $parent) {
+					push @cmd, $par;
+				}
+			}
+			my @revsin = ();
+			my ($revlist, $ctx) = command_output_pipe(@cmd);
+			while (<$revlist>) {
+				my $irev = $_;
+				chomp $irev;
+				my (undef, $csvnrev, undef) =
+					cmt_metadata($irev);
+				unless (defined $csvnrev) {
+					# A child is missing SVN annotations...
+					# this might be OK, or might not be.
+					warn "W:child $irev is merged into revision "
+						 ."$d but does not have git-svn metadata. "
+						 ."This means git-svn cannot determine the "
+						 ."svn revision numbers to place into the "
+						 ."svn:mergeinfo property. You must ensure "
+						 ."a branch is entirely committed to "
+						 ."SVN before merging it in order for "
+						 ."svn:mergeinfo population to function "
+						 ."properly";
+				}
+				push @revsin, $csvnrev;
+			}
+			command_close_pipe($revlist, $ctx);
+
+			last unless $all_parents_ok;
+
+			# We now have a list of all SVN revnos which are
+			# merged by this particular parent. Integrate them.
+			next if $#revsin == -1;
+			my $newmergeinfo = "$branchpath:" . join(',', @revsin);
+			$aggregate_mergeinfo =
+				merge_merge_info($aggregate_mergeinfo,
+								 $newmergeinfo, 1);
+		}
+		if ($all_parents_ok and $aggregate_mergeinfo) {
+			return $aggregate_mergeinfo;
+		}
+	}
+
+	return undef;
+}
+
 sub cmd_dcommit {
 	my $head = shift;
 	command_noisy(qw/update-index --refresh/);
@@ -547,6 +736,62 @@ sub cmd_dcommit {
 		     "without --no-rebase may be required."
 	}
 	my $expect_url = $url;
+
+	my $push_merge_info = eval {
+		command_oneline(qw/config --get svn.pushmergeinfo/)
+		};
+	if (not defined($push_merge_info)
+			or $push_merge_info eq "false"
+			or $push_merge_info eq "no"
+			or $push_merge_info eq "never") {
+		$push_merge_info = 0;
+	}
+
+	unless (defined $_merge_info or not $push_merge_info) {
+		# Preflight check of changes to ensure no issues with mergeinfo
+		# This includes check for uncommitted-to-SVN parents
+		# (other than the first parent, which we will handle),
+		# information from different SVN repos, and paths
+		# which are not underneath this repository root.
+		my $rooturl = $gs->repos_root;
+		foreach my $d (@$linear_refs) {
+			my %parentshash;
+			read_commit_parents(\%parentshash, $d);
+			my @realparents = @{$parentshash{$d}};
+			if ($#realparents > 0) {
+				# Merge commit
+				shift @realparents; # Remove/ignore first parent
+				foreach my $parent (@realparents) {
+					my ($branchurl, $svnrev, $paruuid) = cmt_metadata($parent);
+					unless (defined $paruuid) {
+						# A parent is missing SVN annotations...
+						# abort the whole operation.
+						fatal "$parent is merged into revision $d, "
+							 ."but does not have git-svn metadata. "
+							 ."Either dcommit the branch or use a "
+							 ."local cherry-pick, FF merge, or rebase "
+							 ."instead of an explicit merge commit.";
+					}
+
+					unless ($paruuid eq $uuid) {
+						# Parent has SVN metadata from different repository
+						fatal "merge parent $parent for change $d has "
+							 ."git-svn uuid $paruuid, while current change "
+							 ."has uuid $uuid!";
+					}
+
+					unless ($branchurl =~ /^$rooturl(.*)/) {
+						# This branch is very strange indeed.
+						fatal "merge parent $parent for $d is on branch "
+							 ."$branchurl, which is not under the "
+							 ."git-svn root $rooturl!";
+					}
+				}
+			}
+		}
+	}
+
+	my $rewritten_parent;
 	Git::SVN::remove_username($expect_url);
 	while (1) {
 		my $d = shift @$linear_refs or last;
@@ -561,6 +806,13 @@ sub cmd_dcommit {
 			print "diff-tree $d~1 $d\n";
 		} else {
 			my $cmt_rev;
+
+			unless (defined $_merge_info or not $push_merge_info) {
+				$_merge_info = populate_merge_info($d, $gs, $uuid,
+												   $linear_refs,
+												   $rewritten_parent);
+			}
+
 			my %ed_opts = ( r => $last_rev,
 			                log => get_commit_entry($d)->{log},
 			                ra => Git::SVN::Ra->new($url),
@@ -603,6 +855,9 @@ sub cmd_dcommit {
 				@finish = qw/reset --mixed/;
 			}
 			command_noisy(@finish, $gs->refname);
+
+			$rewritten_parent = command_oneline(qw/rev-parse HEAD/);
+
 			if (@diff) {
 				@refs = ();
 				my ($url_, $rev_, $uuid_, $gs_) =
diff --git a/t/t9160-git-svn-mergeinfo-push.sh b/t/t9160-git-svn-mergeinfo-push.sh
new file mode 100755
index 0000000..216f3d7
--- /dev/null
+++ b/t/t9160-git-svn-mergeinfo-push.sh
@@ -0,0 +1,104 @@
+#!/bin/sh
+#
+# Portions copyright (c) 2007, 2009 Sam Vilain
+# Portions copyright (c) 2011 Bryan Jacobs
+#
+
+test_description='git-svn svn mergeinfo propagation'
+
+. ./lib-git-svn.sh
+
+test_expect_success 'load svn dump' "
+	svnadmin load -q '$rawsvnrepo' \
+	  < '$TEST_DIRECTORY/t9160/branches.dump' &&
+	git svn init --minimize-url -R svnmerge \
+	  -T trunk -b branches '$svnrepo' &&
+	git svn fetch --all
+	"
+
+test_expect_success 'propagate merge information' '
+	git config svn.pushmergeinfo yes &&
+	git checkout svnb1 &&
+	git merge --no-ff svnb2 &&
+	git svn dcommit
+	'
+
+test_expect_success 'check svn:mergeinfo' '
+	mergeinfo=$(svn_cmd propget svn:mergeinfo "$svnrepo"/branches/svnb1)
+	test "$mergeinfo" = "/branches/svnb2:3,8"
+	'
+
+test_expect_success 'merge another branch' '
+	git merge --no-ff svnb3 &&
+	git svn dcommit
+	'
+
+test_expect_success 'check primary parent mergeinfo respected' '
+	mergeinfo=$(svn_cmd propget svn:mergeinfo "$svnrepo"/branches/svnb1)
+	test "$mergeinfo" = "/branches/svnb2:3,8
+/branches/svnb3:4,9"
+	'
+
+test_expect_success 'merge existing merge' '
+	git merge --no-ff svnb4 &&
+	git svn dcommit
+	'
+
+test_expect_success "check both parents' mergeinfo respected" '
+	mergeinfo=$(svn_cmd propget svn:mergeinfo "$svnrepo"/branches/svnb1)
+	test "$mergeinfo" = "/branches/svnb2:3,8
+/branches/svnb3:4,9
+/branches/svnb4:5-6,10-12
+/branches/svnb5:6,11"
+	'
+
+test_expect_success 'make further commits to branch' '
+	git checkout svnb2 &&
+	touch newb2file &&
+	git add newb2file &&
+	git commit -m "later b2 commit" &&
+	touch newb2file-2 &&
+	git add newb2file-2 &&
+	git commit -m "later b2 commit 2" &&
+	git svn dcommit
+	'
+
+test_expect_success 'second forward merge' '
+	git checkout svnb1 &&
+	git merge --no-ff svnb2 &&
+	git svn dcommit
+	'
+
+test_expect_success 'check new mergeinfo added' '
+	mergeinfo=$(svn_cmd propget svn:mergeinfo "$svnrepo"/branches/svnb1)
+	test "$mergeinfo" = "/branches/svnb2:3,8,16-17
+/branches/svnb3:4,9
+/branches/svnb4:5-6,10-12
+/branches/svnb5:6,11"
+	'
+
+test_expect_success 'reintegration merge' '
+	git checkout svnb4 &&
+	git merge --no-ff svnb1 &&
+	git svn dcommit
+	'
+
+test_expect_success 'check reintegration mergeinfo' '
+	mergeinfo=$(svn_cmd propget svn:mergeinfo "$svnrepo"/branches/svnb4)
+	test "$mergeinfo" = "/branches/svnb1:2-4,7-9,13-18
+/branches/svnb2:3,8,16-17
+/branches/svnb3:4,9
+/branches/svnb4:5-6,10-12
+/branches/svnb5:6,11"
+	'
+
+test_expect_success 'dcommit a merge at the top of a stack' '
+	git checkout svnb1 &&
+	touch anotherfile &&
+	git add anotherfile &&
+	git commit -m "a commit" &&
+	git merge svnb4 &&
+	git svn dcommit
+	'
+
+test_done
diff --git a/t/t9160/branches.dump b/t/t9160/branches.dump
new file mode 100644
index 0000000..e61c3e7
--- /dev/null
+++ b/t/t9160/branches.dump
@@ -0,0 +1,374 @@
+SVN-fs-dump-format-version: 2
+
+UUID: 1ef08553-f2d1-45df-b38c-19af6b7c926d
+
+Revision-number: 0
+Prop-content-length: 56
+Content-length: 56
+
+K 8
+svn:date
+V 27
+2011-09-02T16:08:02.941384Z
+PROPS-END
+
+Revision-number: 1
+Prop-content-length: 114
+Content-length: 114
+
+K 7
+svn:log
+V 12
+Base commit
+
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:08:27.205062Z
+PROPS-END
+
+Node-path: branches
+Node-kind: dir
+Node-action: add
+Prop-content-length: 10
+Content-length: 10
+
+PROPS-END
+
+
+Node-path: trunk
+Node-kind: dir
+Node-action: add
+Prop-content-length: 10
+Content-length: 10
+
+PROPS-END
+
+
+Revision-number: 2
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 19
+Create branch svnb1
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:09:43.628137Z
+PROPS-END
+
+Node-path: branches/svnb1
+Node-kind: dir
+Node-action: add
+Node-copyfrom-rev: 1
+Node-copyfrom-path: trunk
+
+
+Revision-number: 3
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 19
+Create branch svnb2
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:09:46.339930Z
+PROPS-END
+
+Node-path: branches/svnb2
+Node-kind: dir
+Node-action: add
+Node-copyfrom-rev: 1
+Node-copyfrom-path: trunk
+
+
+Revision-number: 4
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 19
+Create branch svnb3
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:09:49.394515Z
+PROPS-END
+
+Node-path: branches/svnb3
+Node-kind: dir
+Node-action: add
+Node-copyfrom-rev: 1
+Node-copyfrom-path: trunk
+
+
+Revision-number: 5
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 19
+Create branch svnb4
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:09:54.114607Z
+PROPS-END
+
+Node-path: branches/svnb4
+Node-kind: dir
+Node-action: add
+Node-copyfrom-rev: 1
+Node-copyfrom-path: trunk
+
+
+Revision-number: 6
+Prop-content-length: 121
+Content-length: 121
+
+K 7
+svn:log
+V 19
+Create branch svnb5
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:09:58.602623Z
+PROPS-END
+
+Node-path: branches/svnb5
+Node-kind: dir
+Node-action: add
+Node-copyfrom-rev: 1
+Node-copyfrom-path: trunk
+
+
+Revision-number: 7
+Prop-content-length: 110
+Content-length: 110
+
+K 7
+svn:log
+V 9
+b1 commit
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:10:20.292369Z
+PROPS-END
+
+Node-path: branches/svnb1/b1file
+Node-kind: file
+Node-action: add
+Prop-content-length: 10
+Text-content-length: 0
+Text-content-md5: d41d8cd98f00b204e9800998ecf8427e
+Text-content-sha1: da39a3ee5e6b4b0d3255bfef95601890afd80709
+Content-length: 10
+
+PROPS-END
+
+
+Revision-number: 8
+Prop-content-length: 110
+Content-length: 110
+
+K 7
+svn:log
+V 9
+b2 commit
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:10:38.429199Z
+PROPS-END
+
+Node-path: branches/svnb2/b2file
+Node-kind: file
+Node-action: add
+Prop-content-length: 10
+Text-content-length: 0
+Text-content-md5: d41d8cd98f00b204e9800998ecf8427e
+Text-content-sha1: da39a3ee5e6b4b0d3255bfef95601890afd80709
+Content-length: 10
+
+PROPS-END
+
+
+Revision-number: 9
+Prop-content-length: 110
+Content-length: 110
+
+K 7
+svn:log
+V 9
+b3 commit
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:10:52.843023Z
+PROPS-END
+
+Node-path: branches/svnb3/b3file
+Node-kind: file
+Node-action: add
+Prop-content-length: 10
+Text-content-length: 0
+Text-content-md5: d41d8cd98f00b204e9800998ecf8427e
+Text-content-sha1: da39a3ee5e6b4b0d3255bfef95601890afd80709
+Content-length: 10
+
+PROPS-END
+
+
+Revision-number: 10
+Prop-content-length: 110
+Content-length: 110
+
+K 7
+svn:log
+V 9
+b4 commit
+K 10
+svn:author
+V 7
+bjacobs
+K 8
+svn:date
+V 27
+2011-09-02T16:11:17.489870Z
+PROPS-END
+
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-- 
1.7.6.1.5.g8ba83.dirty