Allow branch deletions to be pushed in Mercurial
Summary: Fixes T5050. This might not be 100% right in all edge cases, but it worked on everything I tried.
Test Plan:
- Pushed a branch deletion.
- Pushed a branch creation.
- Pushed a brnach creation + deletion.
- Pushed a brnach deletion + creation.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5050
Differential Revision: https://secure.phabricator.com/D9122