anchor.diff:  Highlighters are often defined for a specific filetype, and it makes then sense to
   share the highlighters between all the windows on the same filetypes.
   
  -A shared highlighter can be defined with
  -
  ------------------------
  -defhl <shared_hl_name>
  ------------------------
  -
  -Highlighters can be added to it using the regular +:addhl+ command, with the
  -+-def-group <shared_hl_name>+ option.
  +A shared highlighter can be defined with the +:addhl+ command
  +
  +------------------------------
  +addhl -group /<group_name> ...
  +------------------------------
  +
  +when the group switch values starts with a '/', it references a group in the
  +shared highlighters, rather than the window highlighters.
  +
  +The common case would be to create a named shared group, and then fill it
  +with highlighters:
  +
  +---------------------------
  +addhl -group / group <name>
  +addhl -group /name regex ...
  +---------------------------
   
   It can then be referenced in a window using the +ref+ highlighter.
   
  ---------------------------
  -addhl ref <shared_hl_name>
  ---------------------------
  +----------------
  +addhl ref <name>
  +----------------
  +
  +the +ref+ can reference any named highlighter in the shared namespace.
   
   Hooks
   -----
  
positive.code: :rmhl <highlighter_id>
  ----------------------
  
  existing highlighters are:
  
   * +number_lines+: show line numbers
   * +group <group_name>+: highlighter group, containing other highlighters.
         useful when multiple highlighters work together and need to be
         removed as one. Adding and removing from a group can be done using
         `:addhl -group <group> <highlighter_name> <highlighter_parameters...>`
         `:rmhl  -group <group> <highlighter_name>`
   * +regex <ex> <color>...+: highlight a regex, takes the regex as first parameter,
         followed by any number of color parameters. color format is:
         <capture_id>:<fg_color>[,<bg_color>]
  
negative.code: 
  the +:edit+ command can take a -fifo parameter:
  
  ---------------------------------------------
  :edit -fifo <filename> [-scroll] <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.
  
  if the +-scroll+ switch is specified, the initial cursor position will be made
  such as the window displaying the buffer will scroll as new data is read.
  
  This is very useful for running some commands asynchronously while displaying
  their result in a buffer. See rc/make.kak and rc/grep.kak for examples.
  