etcdserver/api/v2v3/store.go
func (s *v2v3Store) mkPathDepth(nodePath string, depth int) string {
	normalForm := path.Clean(path.Join("/", nodePath))
	n := strings.Count(normalForm, "/") + depth
	return fmt.Sprintf("%s/%03d/k/%s", s.pfx, n, normalForm)
}
func (s *v2v3Store) mkPathDepth(nodePath string, depth int) string {
	normalForm := path.Clean(path.Join("/", nodePath))
	n := strings.Count(normalForm, "/") + depth
	return fmt.Sprintf("%s/%03d/k/%s", s.pfx, n, normalForm)
}
// mkPathDepth makes a path to a key that encodes its directory depth
// for fast directory listing. If a depth is provided, it is added
// to the computed depth.