Update "AffectedPath" table when a revision's repository changes
Ref T13639. There's currently a hard-to-hit bug where editing the "Repository" of a revision doesn't update this index.
Instead: update the index on repository change, not just diff update.
- Updated a revision, used debug view to see index update.
- Changed repository on a revision, used debug view to see index update.
Maniphest Tasks: T13639
Differential Revision: https://secure.phabricator.com/D21618