kernel-rebase: add simple caching for patches list

This change adds a simple Pickle-based cache for patches list, which
often takes a while to regerenare, but doesn't change within release. This change
speeds up consecutive runs significantly.

BUG=None
TEST=./bisect_branch.py

Change-Id: I4856569da76db920255d315762abc77acce4b9f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/4269554
Tested-by: Łukasz Bartosik <ukaszb@google.com>
Commit-Queue: Łukasz Bartosik <ukaszb@google.com>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
1 file changed