gitweb: Fix bug in evaluate_path_info

There was bug in parsing "project/:/file" and "project/:/" path_info
URLs, with implicit HEAD as 'hash_base'.

For such URLs the refname is empty, and before this fix regexp for
parsing path_info fragment assumed that it is always non-empty.

Refname cannot contain ':', as per 'git check-ref-format'.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -780,10 +780,10 @@ sub evaluate_path_info {
 		'history',
 	);
 
-	# we want to catch
+	# we want to catch, among others
 	# [$hash_parent_base[:$file_parent]..]$hash_parent[:$file_name]
 	my ($parentrefname, $parentpathname, $refname, $pathname) =
-		($path_info =~ /^(?:(.+?)(?::(.+))?\.\.)?(.+?)(?::(.+))?$/);
+		($path_info =~ /^(?:(.+?)(?::(.+))?\.\.)?([^:]+?)?(?::(.+))?$/);
 
 	# first, analyze the 'current' part
 	if (defined $pathname) {