In the case of ref deletion, the null sha is not very unique, and could be present in another project. Make sure to compare the project, ref, and sha to determine if two ref-updated events are equal. Change-Id: I6bd4a02f21bd31b91ef369783641ded014f7717c Reviewed-on: https://review.openstack.org/13839 Reviewed-by: Monty Taylor <mordred@inaugust.com> Reviewed-by: Clark Boylan <clark.boylan@gmail.com> Approved: James E. Blair <corvus@inaugust.com> Tested-by: Jenkins