anchor.diff:  
   -behaviour(gen_server).
   
  --export([start_link/0, get_entity/2, get_entity/3, get_tag/1, get_branch/1, put_entity/3, put_entity/4, put_tag/2, put_tag/4, put_branch/2, put_branch/4, get_meta/2, get_meta/1, put_meta/3, list_meta/0, list_entities/1, list_entities/2, list_tags/0, list_branches/0, version/0, version_string/0, delete_tag/1, delete_branch/1, delete_entity/3]).
  +-export([start_link/0, get_entity/2, get_entity/3, get_tag/1, get_branch/1, put_entity/3, put_entity/4, put_tag/2, put_tag/4, put_branch/2, put_branch/4, get_meta/2, get_meta/1, put_meta/3, list_meta/0, list_entities/1, list_entities/2, list_tags/0, list_branches/0, version/0, version_string/0, delete_tag/1, delete_branch/1, delete_entity/3, delete_meta/2]).
   
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
   
  
positive.code:     ok.
  
  delete_helper(Name, Kind, Commit, StoreMod) ->
      ok.
  
  immediately_affected_entities(_Name, node, _Tree, _StoreMod) ->
      % removing a node doesn't affect anything else
  
negative.code: elim_param(DelP, {wallaby_subsystem, _}=Obj) ->
      wallaby_subsystem:set_parameters(Obj, [P || P <- wallaby_subsystem:parameters(Obj),
  						P =/= DelP]).
  
  handle_info(_X, State) ->
      {noreply, State}.
  