Fix an issue with Diffusion's display of copied files in Git

Summary: If a change copies some file A to B and also edits A, we currently record this as an indirect change and don't show the edits to A in the diff. Instead, record these as direct changes.

Test Plan: Created two commits, one which copied A to B without modifying A and one which copied A to B and modified A. Viewed both commits in Diffusion. The unmodified commit did not show A, and the modified commit did (with the correct changes).

Reviewers: btrahan, vrana

Reviewed By: vrana

CC: champo, aran

Differential Revision: https://secure.phabricator.com/D3120