implement access control which is finer grained than the one
based on filesystem group.
-The standard output of this hook is sent to `/dev/null`; if you
+The standard output of this hook is sent to `stderr`, so if you
want to report something to the `git-send-pack` on the other end,
-you can redirect your output to your `stderr`.
+you can simply `echo` your messages.
post-update