Summary: Ref T4292. This will let the UI and future `bin/repository` tools give administrators more tools to understand problems when reporting or resolving them.
Test Plan:
- Pushed fully clean repository.
- Pushed previously-pushed repository.
- Forced write to abort, inspected useful information in the database.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4292
Differential Revision: https://secure.phabricator.com/D15748
