anchor.diff:  
   %%--------------------------------------------------------------------
   %% @doc
  +%% Clones a mstore, removing currently open files form it.
  +%% @end
  +%%--------------------------------------------------------------------
  +-spec clone(mstore()) -> mstore().
  +
  +clone(MStore = #mstore{files=[]}) ->
  +    MStore;
  +clone(MStore) ->
  +    MStore#mstore{files=[]}.
  +
  +%%--------------------------------------------------------------------
  +%% @doc
   %% Recursively deletes a metric set.
   %% @end
   %%--------------------------------------------------------------------
  
positive.code: -module(mstore).
  
  -export([
           new/2,
           open/1,
           open/2,
  
negative.code:     close(MStore),
      case file:list_dir(Dir) of
          {ok, Files} ->
              Files1 = [filename:join([Dir, File]) || File <- Files],
              [file:delete(F) || F <- Files1],
              file:del_dir(Dir);
          {error, enoent} ->
  