anchor.diff:  -behaviour(gen_server).
   
   %% API
  --export([commit/0, abort/0, abort/1,add_files/1, start_preview_server/0]).
  +-export([commit/0, abort/0,add_files/1, start_preview_server/0]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code: 				  throw(Err1)
       			  end,
       			  case F1==F2 of 
       			      true -> ok;
       			      false ->
       				  case file:rename(F1, F2) of 
       				      ok -> ok;
  
negative.code: 
  %%-spec(abort/0::() ->{ok, [filename()]}).
  
  abort() ->
      gen_server:call(wrangler_preview_server, abort).
     
  