Since ~2002, Macports has used svn or git, but users, by default, rsync the complete port definitions + a server-generated index + a signature.

The index is used for all lookups; it can also be generated or incrementally updated client-side to accommodate local changes.

This has worked fine for literally decades, starting back when bandwidth and CPU power was far more limited.

The problem isn’t using SCM, and the solutions have been known for a very long time.