anchor.diff:   * _?_: search (extend to next match)
    * _n_: select next match
    * _N_: add a new selection with next match
  - * _alt-n_: replace last selection with next match (preserving the others)
  -
  - * _alt-c_: center last selection in current window
  + * _alt-n_: replace main selection with next match (preserving the others)
  +
  + * _alt-c_: center main selection in current window
    * _pageup_: scroll up
    * _pagedown_: scroll down
   
  
positive.code: 
  Some of kakoune state is available through environment variables:
  
   * +kak_selection+: content of the last selection
   * +kak_bufname+: name of the current buffer
   * +kak_timestamp+: timestamp of the current buffer, the timestamp is an
         integer value which is incremented each time the buffer is modified.
  
negative.code: 
  registers are named list of text. They are used for various purpose, like
  storing the last yanked test, or the captures groups associated with the
  selections.
  
  While in insert mode, ctrl-r followed by a register name (one character)
  inserts it.
  