git-svn: memoize conversion of SVN merge ticket info to git commit ranges

Each time the svn mergeinfo ticket changes, we look it up in the rev_map;
when there are a lot of merged branches, this will result in many repeated
lookups of the same information for subsequent commits.  Arrange the slow
part of the function so that it may be memoized, and memoize it.  The more
expensive revision walking operation can be memoized separately.

[ew: changed "next" to "return" for function exit]

Signed-off-by: Sam Vilain <sam@vilain.net>
Acked-by: Eric Wong <normalperson@yhbt.net>

git-svn.perl

@@ -1634,6 +1634,7 @@ use Carp qw/croak/;
 use File::Path qw/mkpath/;
 use File::Copy qw/copy/;
 use IPC::Open3;
+use Memoize;  # core since 5.8.0, Jul 2002
 
 my ($_gc_nr, $_gc_period);
 
@@ -2994,6 +2995,55 @@ sub find_extra_svk_parents {
 	}
 }
 
+sub lookup_svn_merge {
+	my $uuid = shift;
+	my $url = shift;
+	my $merge = shift;
+
+	my ($source, $revs) = split ":", $merge;
+	my $path = $source;
+	$path =~ s{^/}{};
+	my $gs = Git::SVN->find_by_url($url.$source, $url, $path);
+	if ( !$gs ) {
+		warn "Couldn't find revmap for $url$source\n";
+		return;
+	}
+	my @ranges = split ",", $revs;
+	my ($tip, $tip_commit);
+	my @merged_commit_ranges;
+	# find the tip
+	for my $range ( @ranges ) {
+		my ($bottom, $top) = split "-", $range;
+		$top ||= $bottom;
+		my $bottom_commit =
+			$gs->rev_map_get($bottom, $uuid) ||
+			$gs->rev_map_get($bottom+1, $uuid);
+		my $top_commit;
+		for (; !$top_commit && $top >= $bottom; --$top) {
+			$top_commit =
+				$gs->rev_map_get($top, $uuid);
+		}
+
+		unless ($top_commit and $bottom_commit) {
+			warn "W:unknown path/rev in svn:mergeinfo "
+				."dirprop: $source:$range\n";
+			next;
+		}
+
+		push @merged_commit_ranges,
+			"$bottom_commit..$top_commit";
+
+		if ( !defined $tip or $top > $tip ) {
+			$tip = $top;
+			$tip_commit = $top_commit;
+		}
+	}
+	return ($tip_commit, @merged_commit_ranges);
+}
+BEGIN {
+	memoize 'lookup_svn_merge';
+}
+
 # note: this function should only be called if the various dirprops
 # have actually changed
 sub find_extra_svn_parents {
@@ -3008,44 +3058,11 @@ sub find_extra_svn_parents {
 	my @merge_tips;
 	my @merged_commit_ranges;
 	my $url = $self->rewrite_root || $self->{url};
+	my $uuid = $self->ra_uuid;
 	for my $merge ( @merges ) {
-		my ($source, $revs) = split ":", $merge;
-		my $path = $source;
-		$path =~ s{^/}{};
-		my $gs = Git::SVN->find_by_url($url.$source, $url, $path);
-		if ( !$gs ) {
-			warn "Couldn't find revmap for $url$source\n";
-			next;
-		}
-		my @ranges = split ",", $revs;
-		my ($tip, $tip_commit);
-		# find the tip
-		for my $range ( @ranges ) {
-			my ($bottom, $top) = split "-", $range;
-			$top ||= $bottom;
-			my $bottom_commit =
-				$gs->rev_map_get($bottom, $self->ra_uuid) ||
-				$gs->rev_map_get($bottom+1, $self->ra_uuid);
-			my $top_commit;
-			for (; !$top_commit && $top >= $bottom; --$top) {
-				$top_commit =
-					$gs->rev_map_get($top, $self->ra_uuid);
-			}
-
-			unless ($top_commit and $bottom_commit) {
-				warn "W:unknown path/rev in svn:mergeinfo "
-					."dirprop: $source:$range\n";
-				next;
-			}
-
-			push @merged_commit_ranges,
-				"$bottom_commit..$top_commit";
-
-			if ( !defined $tip or $top > $tip ) {
-				$tip = $top;
-				$tip_commit = $top_commit;
-			}
-		}
+		my ($tip_commit, @ranges) =
+			lookup_svn_merge( $uuid, $url, $merge );
+		push @merged_commit_ranges, @ranges;
 		unless (!$tip_commit or
 				grep { $_ eq $tip_commit } @$parents ) {
 			push @merge_tips, $tip_commit;