distgit: Block push of branches named 'origin/*'

We already use the update hook for gitolite.

This introduces a new update hook, which merely chains the gitolite one,
and a new one to block pushes to badly named branches.

The new hook was written originally by Till Maas.

https://fedorahosted.org/rel-eng/ticket/4071

roles/git/hooks/tasks/main.yml

@@ -13,6 +13,8 @@
   with_items:
   - post-receive-fedmsg
   - post-receive-chained
+  - update-block-push-origin
+  - update-chained
 
 - name: install the git mail hooks
   copy: src={{item}} dest=/usr/share/git-core/mail-hooks mode=0755