Commands: Undo-Migration

Resolves #631

Verification: Manual bashing. Will cover in functionals.
We discussed possible confusion in what do in various cases. "Unapply" is probably one of those cases where just saying Unapply may not be enough information for me to know what to do. Don't block on this for this code review, but we should consider how to best help people know what to do in various situations that they get into.