0861ed9d1ff816aae6d973f67ce85f1fbf9afecf

Treat empty hook values as missing, rather than executing the path called "". Use changeMergedHook instead of changeMerged, to match the rest of the hooks and the documentation. Change-Id: Ide7ddd57d5ef3f45dad815d9bf7c4cda76c49f6c
Description
RETIRED, Gerrit as used by OpenStack