gitweb: Make use of $PATH_INFO for project parameter

Allow to have project name in the path part of URL, just after the name of
script. For example instead of gitweb.cgi?p=git.git you can write
gitweb.cgi/git.git or gitweb.cgi/git.git/

Not used in URLs inside gitweb; it means that the above alternate syntax
must be generated by hand, at least for now.

Side effect: project name parameter is now stripped of leading and
trailing slash before validation.

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

gitweb/gitweb.cgi

@@ -86,8 +86,9 @@ if (defined $order) {
 	}
 }
 
-my $project = $cgi->param('p');
+my $project = ($cgi->param('p') || $ENV{'PATH_INFO'});
 if (defined $project) {
+	$project =~ s|^/||; $project =~ s|/$||;
 	$project = validate_input($project);
 	if (!defined($project)) {
 		die_error(undef, "Invalid project parameter.");