Summary:
Ref T10010. This does some cleanups on the schema:
- `viewPolicy`, `editPolicy` and `joinPolicy` were nullable, but should never be `null`. Set them to defaults if they're null, then make the column non-nullable.
- Rename `phrictionSlug` to `primarySlug` and stop adding and removing trailing slashes from it.
- Add new columns to support milestones and non-milestone subprojects.
- Drop very old subprojectPHIDs column. This hasn't done anything in the UI for years and years, and isn't particularly realistic to migrate forward.
The new columns aren't reachable from the UI.
Test Plan:
- Applied patches.
- Grepped for `phrictionSlug`.
- Grepped for `subprojectPHIDs`.
- Created tasks.
- Edited tasks.
- Verified existing tasks still had primary slugs.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10010
Differential Revision: https://secure.phabricator.com/D14825
