Cache repository clone

Now, we are doing a full clone of the repository, this can be a pain when the repository is a big one. We need to find a way to cache, avoid a full clone each time.
There is a concern about privacy & worker, so the subject is not easy, maybe rely on Cache from WorkerDirectory?

The issue names no files or tests. Start by locating the code path that performs the full repository clone, then investigate whether WorkerDirectory can provide a privacy-safe cache. Done means repeated clones avoid unnecessary full downloads without compromising worker privacy.

Written by the indexing model from the issue text.