R1:2a83df578604

Fix an issue where a GROUP BY was missing when a query matched a revision using multiple hashes

Summary:
Ref T13581. If you query for revisions by hash and provide multiple hashes (A, B) which match a single revision (e.g., older and newer diffs for that revision), the query omits a GROUP BY clause but should contain one.

Add a GROUP BY clause in this case.

Test Plan:
With a working copy that has multiple hashes corresponding to a single revision, ran `arc branches` before and after the change. Before…