gitweb: use for-each-ref to show the latest activity across branches

The project list page shows last change from the HEAD branch but
often people would want to view activity on any branch.

Unfortunately that is fairly expensive without the core-side
support.  for-each-ref was invented exactly for that.

Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -1009,6 +1009,24 @@ sub parse_tag {
 	return %tag
 }
 
+sub git_get_last_activity {
+	my ($path) = @_;
+	my $fd;
+
+	$git_dir = "$projectroot/$path";
+	open($fd, "-|", git_cmd(), 'for-each-ref',
+	     '--format=%(refname) %(committer)',
+	     '--sort=-committerdate',
+	     'refs/heads') or return;
+	my $most_recent = <$fd>;
+	close $fd or return;
+	if ($most_recent =~ / (\d+) [-+][01]\d\d\d$/) {
+		my $timestamp = $1;
+		my $age = time - $timestamp;
+		return ($age, age_string($age));
+	}
+}
+
 sub parse_commit {
 	my $commit_id = shift;
 	my $commit_text = shift;
@@ -2258,16 +2276,11 @@ sub git_project_list {
 		die_error(undef, "No projects found");
 	}
 	foreach my $pr (@list) {
-		my $head = git_get_head_hash($pr->{'path'});
-		if (!defined $head) {
-			next;
-		}
-		$git_dir = "$projectroot/$pr->{'path'}";
-		my %co = parse_commit($head);
-		if (!%co) {
+		my (@aa) = git_get_last_activity($pr->{'path'});
+		unless (@aa) {
 			next;
 		}
-		$pr->{'commit'} = \%co;
+		($pr->{'age'}, $pr->{'age_string'}) = @aa;
 		if (!defined $pr->{'descr'}) {
 			my $descr = git_get_project_description($pr->{'path'}) || "";
 			$pr->{'descr'} = chop_str($descr, 25, 5);
@@ -2317,7 +2330,7 @@ sub git_project_list {
 		      "</th>\n";
 	}
 	if ($order eq "age") {
-		@projects = sort {$a->{'commit'}{'age'} <=> $b->{'commit'}{'age'}} @projects;
+		@projects = sort {$a->{'age'} <=> $b->{'age'}} @projects;
 		print "<th>Last Change</th>\n";
 	} else {
 		print "<th>" .
@@ -2339,8 +2352,8 @@ sub git_project_list {
 		                        -class => "list"}, esc_html($pr->{'path'})) . "</td>\n" .
 		      "<td>" . esc_html($pr->{'descr'}) . "</td>\n" .
 		      "<td><i>" . chop_str($pr->{'owner'}, 15) . "</i></td>\n";
-		print "<td class=\"". age_class($pr->{'commit'}{'age'}) . "\">" .
-		      $pr->{'commit'}{'age_string'} . "</td>\n" .
+		print "<td class=\"". age_class($pr->{'age'}) . "\">" .
+		      $pr->{'age_string'} . "</td>\n" .
 		      "<td class=\"link\">" .
 		      $cgi->a({-href => href(project=>$pr->{'path'}, action=>"summary")}, "summary")   . " | " .
 		      $cgi->a({-href => href(project=>$pr->{'path'}, action=>"shortlog")}, "shortlog") . " | " .