gitweb: Add support to Link: tag

The tip tree is the one of major subsystem tree in the
Linux kernel project. On the tip tree, the Link: (or
similar Buglink:) tag is used for tracking the original
discussion or context. Since it's ususally in the S-o-b
area, it'd be better using same style with others.

Also as it tends to contain a message-id sent from git
send-email, a part of the line would set a wrong hyperlink
like [1]. Fix it by not using format_log_line_html().

[1] git.kernel.org/?p=linux/kernel/git/tip/tip.git;a=commit;h=08942f6d5d992e9486b07653fd87ea8182a22fa0

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -4470,6 +4470,16 @@ sub git_print_log {
 			next;
 		}
 
+		if ($line =~ m,\s*([a-z]*link): (https?://\S+),i) {
+			if (! $opts{'-remove_signoff'}) {
+				print "<span class=\"signoff\">" . esc_html($1) . ": " .
+					"<a href=\"" . esc_html($2) . "\">" . esc_html($2) . "</a>" .
+					"</span><br/>\n";
+				$skip_blank_line = 1;
+			}
+			next;
+		}
+
 		# print only one empty line
 		# do not print empty line after signoff
 		if ($line eq "") {