Rails repository migrations should use the ReplicateRepository RPC
Data transfers on the Rails side use a different RPC than Gitaly/Praefect would use for data transfers. With the Replicate Repository RPC we're trying to standardize to one RPC to rule them all.
Gitlab::Git::Repository#fetch_internal_remote is used through the
UpdateRepositoryStorageService. The RPC itself doesn't have client side support yet, which should also be added.