code: func (ref Ref) HasPrefix(other Ref) bool {
  	if len(other) > len(ref) {
  		return false
  	}
  	for i := range other {
  		if !ref[i].Equal(other[i]) {
  			return false
  		}
  	}
  	return true
  }
docs: // HasPrefix returns true if the other ref is a prefix of this ref.