* If the input revision starts with refs/ use it as the ref of the CP.
* If the input revision is of the form origin/X, use refs/heads/X as the
  ref of the CP.

Change-Id: I048883afcfe1593e877c004729f859921910c993
Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: build_limited
Recipe-Nontrivial-Roll: chrome_release
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3165297Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Garrett Beaty <gbeaty@google.com>