Implement PhabricatorApplicationTransactionInterface in Differential
Summary:
Ref T4810. Ultimate goal is to let Harbormaster post a "build passed/failed" transaction. To prepare for that, implement PhabricatorApplicationTransactionInterface in Differential.
To allow Harbormaster to take action on diffs but have the transactions apply to revisions, I added a new method so that objects can redirect transactions to some other object.
Test Plan:
- Subscribed/unsubscribed/attached/detached from Differential, saw transactions appear properly.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T4810
Differential Revision: https://secure.phabricator.com/D8802