Default policy for selective sync for files

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### Feature description

As the client works today, if I'd like to sync folder `a/b/c` all the files that live in `/`, `/a/` and `/a/b/` are synced as well.

This can lead to confusion for the user and also unintended local storage capacity usage.

I'd suggest that by default the system shouldn't sync any files that live in levels above of the one selected by the user for sync.