fix: fetch entire change and integration history

Fetching with a specific depth is insufficient and finding the
merge-base is still prone to fail because Git can't resolve the history
between the grafted refspec we start with and whatever the integration
branch is.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: Ie70905f6f5c651022b3ff9e1e56d2eb2177ed7ce
(cherry picked from commit afdcff720185959585c2a1ef970f2caa755e6682)
2 files changed