Merge branch 'stable-3.0' into stable-3.1

* stable-3.0:
  Extend CommitMessageFetcher to handle non-commit objects
  Fix typo in documentation RevUpdatedEvents -> RefUpdatedEvents
  Check if approvals array is null before iterating

Change-Id: I82d25c66ba2f8910390043bf5bdab7e5992a8ec9