We could use the `db.UpdateHead` function here but using that function requires locking `db.vhead`. https://github.com/dgraph-io/badger/blob/158d9271e1052082d6377ffa56483650129b726c/db.go#L674-L691 I could move the lock outside of the function but this would cause contention on the lock. The db.Lock would be held while we're iteration over all the pointers. I prefer to keep it as it is.