branch_util: allow create to accept a manifest file

create-v1 had an option to pass in a local manifest file.
this initially wasn't ported over to the new version.
this quick fix allows this use case. Specifically,
test_manifest needed this functionality.

Bug: b/171724963
Test: Dry runs; unit tests; run_test.sh
Change-Id: Id7f2083c4d4381085294a2a0fa542fff14ac4c6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/go/+/2499293
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
Reviewed-by: Mike Nichols <mikenichols@chromium.org>
Commit-Queue: Julio Hurtado <juahurta@google.com>
Tested-by: Julio Hurtado <juahurta@google.com>
3 files changed