Summary:
Knowing the prepushrebase changeset id is required for retroactive_review.
retroactive_review checks landed commits, but verify_integrity hook runs on a commit before landing. This way the landed commit has no straightforward connection with the original one and retroactive_review can't acknowledge if verify_integrity have seen it.
Reviewed By: krallin
Differential Revision: D27911317
fbshipit-source-id: f7bb0cfbd54fa6ad2ed27fb9d4d67b9f087879f1