ensure we have commits locally before finding common merge-base
Created by: chrispine
Make sure we call ResolveRevision
before we find the common merge-base, in case the commits don't exist locally.
I tested it by creating this campaign:
name: test-3487562349
description: just a random test
importChangesets:
- repository: github.com/sourcegraph/test
externalIDs: [7]
I then added a commit to that PR, went to the campaigns UI, and pressed the "refresh" button. Before this fix, I got the error. After the fix, it correctly refreshed the diff.
Closes #12584.