It's referenced in [the `/compare/` JSON API's output](https://api.github.com/repos/hulu/restfulgit/compare/initial...c04112733fe2db2cb2f179fca1a19365cf15fef5). e.g. https://github.com/hulu/restfulgit/compare/initial...c04112733fe2db2cb2f179fca1a19365cf15fef5.patch
