R1:375400802b7d

Register commits as Diffusion fact objects

Summary:
We will need to process them.
Maybe it will fit better in Repository application but we don't have it yet.

Test Plan:
$ ./fact cursors

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, royw

Differential Revision: https://secure.phabricator.com/D3287