Summary:
Ref T2715. Ref T3551. Ref T603. This does a few things, but they're all sort of small:
- We commonly use a `getX()` / `attachX()` pattern, but have very similar code in the `getX()` method every time. Provide a convenience method to make this pattern easier to write.
- We use `willFilterPage()` in many queries, but it currently is called with zero or more results. This means we have a lot of "if no results, return nothing" boilerplate. Make it call only for one or more results.
- Implement `PhabricatorPolicyInterface` on `ReleephBranch`. A branch has the same policy as its project.
- Implement `ReleephBranchQuery`.
- Move the branch PHID type to application PHID infrastructure.
Test Plan: Browsed Releeph. Used `phid.query` to query branch PHIDs.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T603, T2715, T3551
Differential Revision: https://secure.phabricator.com/D6512
