For snapshot trees, grabbing obsolete snapshots can waste quite a lot of bandwidth and local storage.

A very beneficial optimisation in this case is to check trees in the order of "most recent first", and stop the sync operation as soon as a tree is detected as already being complete locally, or when one has been successfully retrieved from the remote server.

This behaviour will be added as a "sync_latest_only" option, with the current behaviour (mirroring all remote trees, even old ones) remaining the default.