[gclient] Let --revision take repository URLs in addition to local paths.

Pinpoint needs to request builds at specific revisions, e.g. clank@0123 + chromium/src@4567 + v8@89ab. It's not aware of the path of the repositories in the src tree, so it makes more sense to pass in the repository URLs instead.

Bug: https://github.com/catapult-project/catapult/issues/3394

Change-Id: Ib9fb9a7bf5d918c18f37c3b2b36418537512b235
Reviewed-on: https://chromium-review.googlesource.com/520569
Commit-Queue: David Tu <dtu@chromium.org>
Reviewed-by: Paweł Hajdan Jr. <phajdan.jr@chromium.org>

gclient.py

@@ -736,6 +736,8 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
     parsed_url = self.LateOverride(self.url)
     file_list = [] if not options.nohooks else None
     revision_override = revision_overrides.pop(self.name, None)
+    if not revision_override and parsed_url:
+      revision_override = revision_overrides.get(parsed_url.split('@')[0], None)
     if run_scm and parsed_url:
       # Create a shallow copy to mutate revision.
       options = copy.copy(options)