Steps:

1. create a parent task (A), a subtask (B), and an unrelated task (C)
2. on task C, merge in duplicate task B

Expected result:

• B is closed as dupe
• I would've expected parent A to depend on C now

Actual result:

• B is closed as dupe
• but parent A only depends on B, not C

Repro'd on test instance of phabricator:
https://test-lwxgpmm3zrwb.phacility.com/T1