gitweb: improve snapshot error handling

The last check in the second block of checks in the &git_snapshot routine
is never executed because the second to last check is a superset of the
last check.

Switch the order of the last two checks. It has the advantage of giving
clients a more specific reason why they cannot get a snapshot format if
the format they have chosen is disabled.

Signed-off-by: Mark Rada <marada@uwaterloo.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

gitweb/gitweb.perl

@@ -5175,10 +5175,10 @@ sub git_snapshot {
 		die_error(400, "Invalid snapshot format parameter");
 	} elsif (!exists($known_snapshot_formats{$format})) {
 		die_error(400, "Unknown snapshot format");
-	} elsif (!grep($_ eq $format, @snapshot_fmts)) {
-		die_error(403, "Unsupported snapshot format");
 	} elsif ($known_snapshot_formats{$format}{'disabled'}) {
 		die_error(403, "Snapshot format not allowed");
+	} elsif (!grep($_ eq $format, @snapshot_fmts)) {
+		die_error(403, "Unsupported snapshot format");
 	}
 
 	if (!defined $hash) {