Add more information to differential.getdiff

Summary: We need some additional fields to heuristically match revisions to the
working copy in arc.

Test Plan: Executed conduit method, got correct values in fields

Reviewers: btrahan, jungejason

Reviewed By: jungejason

CC: aran, jungejason

Differential Revision: https://secure.phabricator.com/D1347