deprecation warning about old style PATH/ syntax

(this commit will probably get reverted after a suitable period has
elapsed and no one is likely to still be using the old syntax).

Forgetting to change it to NAME/ after is a security issue -- you end up
permitting stuff you don't want to!

This commit allows the old syntax but prints a warning

src/gl-compile-conf

@@ -200,6 +200,8 @@ sub parse_conf_file
 
             # if no ref is given, this PERM applies to all refs
             @refs = qw(refs/.*) unless @refs;
+            # deprecation warning
+            map { warn "WARNING: old syntax 'PATH/' found; please use new syntax 'NAME/'\n" if s(^PATH/)(NAME/) } @refs;
             # fully qualify refs that dont start with "refs/" or "NAME/";
             # prefix them with "refs/heads/"
             @refs = map { m(^(refs|NAME)/) or s(^)(refs/heads/); $_ } @refs;