gitweb: show active project_filter in project_list page header

In the page header of a project_list view with a project_filter
given show breadcrumbs in the page headers showing which directory
it is currently limited to and also containing links to the parent
directories.

Signed-off-by: Bernhard R. Link <brlink@debian.org>
Acked-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -3839,6 +3839,18 @@ sub print_header_links {
 	}
 }
 
+sub print_nav_breadcrumbs_path {
+	my $dirprefix = undef;
+	while (my $part = shift) {
+		$dirprefix .= "/" if defined $dirprefix;
+		$dirprefix .= $part;
+		print $cgi->a({-href => href(project => undef,
+		                             project_filter => $dirprefix,
+		                             action => "project_list")},
+			      esc_html($part)) . " / ";
+	}
+}
+
 sub print_nav_breadcrumbs {
 	my %opts = @_;
 
@@ -3857,6 +3869,8 @@ sub print_nav_breadcrumbs {
 			print " / $opts{-action_extra}";
 		}
 		print "\n";
+	} elsif (defined $project_filter) {
+		print_nav_breadcrumbs_path(split '/', $project_filter);
 	}
 }