R1:d09dd23bd705

Actually push to mirrors

Summary: Fixes T4038. Push repositories to mirrors.

Test Plan: Created a functional mirror of a local: https://github.com/epriestley/poems

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4038

Differential Revision: https://secure.phabricator.com/D7633