post_change_branch_tip after unsuccessful pre_change_branch_tip?

[John Szakmeister]

I was working on getting some hooks into place for our infrastructure,
and ran across an unexpected behavior.  If I raise TipChangeRejected
from a pre_change_branch_tip hook, the commit is rejected as expected.
 However, post_change_branch_tip is still run... which seems
erroneous.  Is this expected behavior?  If so, why?

Thanks!

-John