Readding repos to migrations

For a variety of reasons a users may choose to close a migration PR even though it is not yet complete. Currently we assume this means the feedstock has already been migrated (even if that is not the case). How can we handle this more gracefully? Is there or could there be a way for users to readd their feedstock to the active migration? If so, what would this look like? How can we communicate to users the intended workflow?