Diffusion - move build refs to occur over Conduit

Summary: Ref T2784.

Test Plan: loaded up a git commit with refs and they showed up! loaded up a git commit without revs and nothing showed up.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2784

Differential Revision: https://secure.phabricator.com/D5957