anchor.diff:  insert(Key, ObjHash, State) ->
       insert(Key, ObjHash, State, []).
   
  --spec insert(binary(), binary(), hashtree(), proplist()) -> hashtree().
  +-spec insert(binary(), binary() | tombstone, hashtree(), proplist()) -> hashtree().
  +insert(Key, tombstone, State, Opts) ->
  +    insert(Key, ?TOMBSTONE, State, Opts);
  +
   insert(Key, ObjHash, State, Opts) ->
       Hash = erlang:phash2(Key),
       Segment = Hash rem State#state.segments,
  
positive.code: -include_lib("eunit/include/eunit.hrl").
  -endif.
  
  -define(NUM_SEGMENTS, (1024*1024)).
  -define(WIDTH, 1024).
  -define(MEM_LEVELS, 0).
  
negative.code:             end || {KBin, Diff} <- Delta],
      Keys.
  
  
  key_diff_type({?TOMBSTONE , _}) ->
      tombstone_diff;
  key_diff_type({_ , ?TOMBSTONE}) ->
      tombstone_diff;
  key_diff_type({'$none', _}) ->
      missing;
  key_diff_type({_, '$none'}) ->
  