Geo: snippet repos, they are coming

I'm raising this issue just to track some thoughts on Snippet repositories.

In #39176 (closed) we are adding repositories for snippets. Planned for %12.7 at the moment. Some takeaways of that:

Each snippet will have it's own git repository
Snippets are stored in hashed storage format (had a quick call with @fjsanpedro about that)
A snippet has a user_id, but might or might not belong to a project. Global snippets are accessible at /snippets/<id>, project snippets at /<group>/<project>/snippets/<id>.
Snippet ids are unique, even across projects and the global scope

Besides the fact we'll need to do some manual implementation, I'm seeing the following problems:

Selective sync (on group level) won't be possible for global snippets, unless we would be able to also set selective sync on user level
Anything else?