anchor.diff:          indent (3 leading spaces when indent is 4)
   
    * `|`: pipe each selection through the given external filter program
  -        and replace the selection with it's output.
  +        and replace the selection with its output.
    * `<a-|>`: pipe each selection through the given external filter program
           and ignore its output
   
  
positive.code:  * `<a-j>`: join selected lines
   * `<a-J>`: join selected lines and select spaces inserted
              in place of line breaks
   * `<a-m>`: merge contiguous selections together (works across lines as well)
  
   * `<gt> (>)`: indent selected lines
   * `<a-gt>`: indent selected lines, including empty lines
  
negative.code:             tabstop option or the count parameter for tabstop.
  
   * `<a-)>`: rotate selections content, if specified, the count groups
              selections, so `3<a-)>` rotate (1, 2, 3) and (4, 5, 6)
              independently.
   * `<a-(>`: rotate selections content backwards
  
  