depot_tools supports extracting information from branch name. E.g. if
branch contains fix-\d or bug-\d, commit description will contains
appropriate git footers.

However, such behavior should happen only on initial CL upload. Should
user decide to delete such footer, we shouldn't set bug / fix on any
following PS.

R=ehmaldonado@chromium.org

Bug: 1225663
Change-Id: I66adfdca070083ab66727d132919d47feb7ddd43
Fixed: 1225663
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3010709
Auto-Submit: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Andy Perelson <ajp@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>