code: func (s *CombinedMapSlice) UpsertRecorded(key MergeKeys, l interface{}) error {
  	item, err := s.upsert(key, l)
  	if err != nil {
  		return err
  	}
  	item.SetRecorded(l)
  	return nil
  }
docs: // UpsertRecorded adds l to the slice.  If there is already a value of l sharing
  // l's merge key in the slice for either the local or remote, set l the recorded value
  // Otherwise append a new item to the list with the recorded value.