gitweb: Do not show difftree for merges in "commit" view

Do not show difftree against first parent for merges (commits with
more than one parent) in "commit" view, because it usually is
misleading.  git-show and git-whatchanged doesn't show diff for merges
either.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 15 insertions, 7 deletions

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 040ee71..ebf35a1 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -3572,14 +3572,19 @@ sub git_commit {
 	my %cd = parse_date($co{'committer_epoch'}, $co{'committer_tz'});
 
 	my $parent = $co{'parent'};
+	my $parents = $co{'parents'};
 	if (!defined $parent) {
 		$parent = "--root";
 	}
-	open my $fd, "-|", git_cmd(), "diff-tree", '-r', "--no-commit-id",
-		@diff_opts, $parent, $hash, "--"
-		or die_error(undef, "Open git-diff-tree failed");
-	my @difftree = map { chomp; $_ } <$fd>;
-	close $fd or die_error(undef, "Reading git-diff-tree failed");
+	my @difftree;
+	if (@$parents <= 1) {
+		# difftree output is not printed for merges
+		open my $fd, "-|", git_cmd(), "diff-tree", '-r', "--no-commit-id",
+			@diff_opts, $parent, $hash, "--"
+				or die_error(undef, "Open git-diff-tree failed");
+		@difftree = map { chomp; $_ } <$fd>;
+		close $fd or die_error(undef, "Reading git-diff-tree failed");
+	}
 
 	# non-textual hash id's can be cached
 	my $expires;
@@ -3641,7 +3646,7 @@ sub git_commit {
 	}
 	print "</td>" .
 	      "</tr>\n";
-	my $parents = $co{'parents'};
+
 	foreach my $par (@$parents) {
 		print "<tr>" .
 		      "<td>parent</td>" .
@@ -3663,7 +3668,10 @@ sub git_commit {
 	git_print_log($co{'comment'});
 	print "</div>\n";
 
-	git_difftree_body(\@difftree, $hash, $parent);
+	if (@$parents <= 1) {
+		# do not output difftree/whatchanged for merges
+		git_difftree_body(\@difftree, $hash, $parent);
+	}
 
 	git_footer_html();
 }