Summary: See <https://github.com/facebook/phabricator/issues/596> Broadly, Facebook would like to bring Pull Requests from GitHub into Phabricator. In the long term we can do this properly via Doorkeeper/Nuance, but that's probably a ways off. This seems like a reasonable low-budget compromise for now. I'm a little hesitant to add a ton of parameters to this call, but `repositoryPHID` seems pretty reasonable, and is notable because it also controls default policies. Test Plan: - Created a diff with no repositoryPHID. - Created a diff with a repositoryPHID. - Verified it carried over when the diff was used to create a revision. Reviewers: btrahan Reviewed By: btrahan Subscribers: ptarjan, jamesgpearce, epriestley Differential Revision: https://secure.phabricator.com/D9023