code: def validate_rpc_sha(repo_dir, commit):
      
  
      # Is the commit valid? Just in case the commit is a
      # PR ref, we try both the ref given and the ref prepended
      # with the remote 'origin'.
      try:
          osa_differ.validate_commits(repo_dir, [commit])
      except exceptions.InvalidCommitException:
          log.debug("The reference {c} cannot be found. Prepending "
                    "origin remote and retrying.".format(c=commit))
          commit = 'origin/' + commit
          osa_differ.validate_commits(repo_dir, [commit])
  
      return commit
docs: Validate/update a SHA given for the rpc-openstack repo.