Protection from merge commits

[Pete Zaitcev]

Dear All:

I found that I pushed a merge node into Fedora git (fortunately it was
only on f19 branch, not in Rawhide):

commit 51eec48c20ba57054f17ba29f23e6a0aa36df9a4
Merge: ac36771 f9213a5
Author: Pete Zaitcev <zaitcev at kotori.zaitcev.us>
Date:   Wed Aug 7 12:14:15 2013 -0600

    Merge branch 'f19' of ssh://pkgs.fedoraproject.org/openstack-swift into f19

Thought I was careful about them, but apparently not enough. So, does
anyone have a script that can be attached to git hooks, reliably detects
an attempt to push merge nodes, then bails the push?

Thanks,
-- Pete