8f9e9f58e2c3ad65c30fecbc136b375e7979e7b1

Add a new MergeValidationListener interface which can be used to provide additional validation of commits before they are merged to the git repository. Add a MergeValidators class to invoke the merge validator listeners, and call it from MergeOp before the commit is merged. Add a listener to invoke validation provided by plugins. Change-Id: I325d923f5cc0245b60e86a035329b640c1682d48
Description
RETIRED, Gerrit as used by OpenStack