anchor.diff:  
   -record(state, {bucket :: binary(),
                   key :: binary(),
  +                uuid :: binary(),
                   manifest :: lfs_manifest(),
  -                delete_blocks_remaining :: ordset:ordset(integer()),
  +                delete_blocks_remaining :: ordsets:ordset(integer()),
  +                unacked_deletes=ordsets:new(),
                   mani_pid :: pid(),
                   all_delete_works :: list(pid()),
                   free_deleters :: ordsets:new()}).
  
positive.code:     %% timer
      {next_state, deleting, State}.
  
  deleting(_Event, State) ->
      %% We just received a delete
      %% acknowledgement, so depending
      %% on the value of delete_blocks_remaining
      %% (after removing this element,
      %% stay in the deleting state,
      %% or stop.
      %% If stopping, we should also
      %% sync wait to update the manifest.
      %% Cancel the timer
  
      %% or
      %% {stop, normal, State}.
      {next_state, deleting, State}.
  
  handle_event(_Event, StateName, State) ->
      {next_state, StateName, State}.
  
negative.code: %% Internal functions
  %% ====================================================================
  
  maybe_delete_block(State=#state{free_deleters=[]}) ->
      State;
  maybe_delete_block(State=#state{bucket=Bucket,
                                  key=Key,
                                  uuid=UUID,
                                  free_deleters=[DeleterPid | _RestDeleters],
                                  unacked_deletes=UnackedDeletes,
                                  manifest=#lfs_manifest_v2{
                                      delete_blocks_remaining=DeleteBlocksRemaining
                                      = [BlockID | _RestBlocks]}}) ->
      NewUnackedDeletes = ordsets:add_element(BlockID, UnackedDeletes),
      NewDeleteBlocksRemaining = ordsets:del_element(BlockID, DeleteBlocksRemaining),
      %% start the delete...
      riak_moss_block_server:delete_block(DeleterPid, Bucket, Key, UUID, BlockID),
      State#state{unacked_deletes=NewUnackedDeletes,
                  delete_blocks_remaining=NewDeleteBlocksRemaining}.
  
  finish(_State) ->
      ok.
  
  %% ===================================================================
  %% Test API
  %% ===================================================================
  