forklift: Add ability to use a local pull request from a file

In case a pull request hasn't hit the list yet, this patch adds the
ability to generate a pull request locally and then use the local file
as the forklift source.

Change-Id: I95acb8caddb33c876b976896aca3ba67b01aaa21
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2989673
Reviewed-by: Drew Davenport <ddavenport@chromium.org>
Tested-by: Sean Paul <seanpaul@chromium.org>
Commit-Queue: Sean Paul <seanpaul@chromium.org>
2 files changed