anchor.diff:  -----------------
   
   new commands can be defined using the +def+ command.
  +
   ------------------------------
   :def <command_name> <commands>
   ------------------------------
  +
   <commands> is a string containing the commands to execute
   
   def can also takes some flags:
  
positive.code: accessed through %reg{<register>} and %opt{<option>} syntax.
  
  for example you can display last search pattern with
  -------------
  :echo %reg{/}
  -------------
  
negative.code: -----------
  
  the +edit+ command can take a -fifo parameter:
  
  -----------------------------------
  :edit -fifo <filename> <buffername>
  -----------------------------------
  
  in this case, a buffer named +<buffername>+ is created which reads its content
  from fifo +<filename>+. When the fifo is written to, the buffer is automatically
  updated.
  