This is a reland of 1d6478a5

Original change's description:
> gclient: Require a target ref when applying patches.
> 
> Bug: 956807
> Change-Id: Icfffe965f9f4651f22e8ba32c60133a5620bb350
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1616804
> Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

Bug: 956807
Change-Id: I3de8475a091ce6a2a14ff7dcfb92507a205ef78c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1623594Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>