Return attached hashes from differential.query
Summary: See T693. To do "arc branch" performantly in immutable history repositories, we need to be able to do a single query to identify revisions related by hash. Return hash information to enable this.
Test Plan: Ran differential.query.
Reviewers: btrahan, vrana
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T693
Differential Revision: https://secure.phabricator.com/D2859