gitweb: allow action specialization in page header

An optional -action_extra parameter is given to git_header_html() to
identify a variant of the action that is being displayed. For example,
this can be used to specify that the remotes view is being used for a
specific remote and not to display all remotes.

When -action_extra is provided, the action name in the header will be
turned into a link to the action without any arguments or parameters, to
provide a quick link to the non-specific variant of the action.

Signed-off-by: Giuseppe Bilotta <giuseppe.bilotta@gmail.com>
Acked-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -3526,7 +3526,15 @@ EOF
 	if (defined $project) {
 		print $cgi->a({-href => href(action=>"summary")}, esc_html($project));
 		if (defined $action) {
-			print " / $action";
+			my $action_print = $action ;
+			if (defined $opts{-action_extra}) {
+				$action_print = $cgi->a({-href => href(action=>$action)},
+					$action);
+			}
+			print " / $action_print";
+		}
+		if (defined $opts{-action_extra}) {
+			print " / $opts{-action_extra}";
 		}
 		print "\n";
 	}