This hook can be used to prevent 'forced' update on certain refs by
making sure that the object name is a commit object that is a
descendant of the commit object named by the old object name.
-That is, to enforce a "fast forward only" policy.
+That is, to enforce a "fast-forward only" policy.
It could also be used to log the old..new status. However, it
does not know the entire set of branches, so it would end up