code: func (r *Store) MountPoints() []string {
  	mps := make([]string, 0, len(r.mounts))
  	for k := range r.mounts {
  		mps = append(mps, k)
  	}
  	sort.Sort(sort.Reverse(store.ByPathLen(mps)))
  	return mps
  }
docs: // MountPoints returns a sorted list of mount points. It encodes the logic that
  // the longer a mount point the more specific it is. This allows to "shadow" a
  // shorter mount point by a longer one.