Summary:
Depends on D19181. Ref T11015. This nukes duplicates from the table if they exist, then adds a unique key.
(Duplicates should not exist and can not be added with any recent version of the web UI.)
Test Plan:
- Tried to add duplicates with web UI, didn't have any luck.
- Explicitly added duplicates with manual `INSERT`s.
- Viewed packages in web UI and saw duplicates.
- Ran migrations, got a clean purge and a nice unique key.
- There's still no way to actually hit a duplicate key error in the UI (unless you can collide hashes, I suppose), this is purely a correctness/robustness change.
Maniphest Tasks: T11015
Differential Revision: https://secure.phabricator.com/D19182
