anchor.diff:  
   existing highlighters are:
   
  - * +highlight_selections+: used to make current selection visible
  - * +expand_tabs+: expand tabs to next 8 multiple column (to make configurable)
    * +number_lines+: show line numbers
  - * +group+: highlighter group, containing other highlighters. takes one
  -            parameter, <group_name>. 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+: highlight a regex, takes the regex as first parameter, followed by
  -            any number of color spec parameters.
  -            color spec format is: <capture_id>:<fg_color>[,<bg_color>]
  -            For example: `:addhl regex //(\h+TODO:)?[^\n]+ 0:cyan 1:yellow,red`
  -            will highlight C++ style comments in cyan, with an eventual
  -            'TODO:' in yellow on red background.
  + * +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>]
  +       For example: `:addhl regex //(\h+TODO:)?[^\n]+ 0:cyan 1:yellow,red`
  +       will highlight C++ style comments in cyan, with an eventual 'TODO:' in
  +       yellow on red background.
  + * +search <color>+: highlight every matches to the current search pattern. takes
  +       one parameter for the color to apply to highlighted elements.
  + * +flag_lines <flag> <option_name>+: add a column in front of text, and display the
  +       given flag in it for everly lines contained in the int-list option named
  +       <option_name>.
   
   Filters
   -------
  
positive.code:  * +eval [-client <name>] <command>+: execute <command> as if entered in command line
        if client if specified, exec command in the named client context.
   * +echo <text>+: show <text> in status line
   * +set{b,w,g} <option> <value>+: set <option> to <value> in *b*uffer, *w*indow
        or *g*lobal scope.
   * +c[ol]a[lias] <name> <colspec>+: define a color alias, so that name can be
        used instead of colspec in contexts where a color is needed.
   * +nop+: does nothing, but as with every other commands, arguments may be
  
negative.code: Object Selection
  ----------------
  
  Some keys allow you to select a text object:
  
   * _alt-a_: selects the whole object
   * _alt-i_: selects the inner object, that is the object excluding it's surrounder.
              for example, for a quoted string, this will not select the quote, and
              for a word this will not select trailing spaces.
   * _[_: selects to object start
   * _]_: selects to object end
  
  After this key, you need to enter a second key in order to specify which
  object you want.
  
   * _b_, _(_ or _)_: select the enclosing parenthesis
   * _B_, _{_ or _}_: select the enclosing {} block
   * _[_ or _]_: select the enclosing [] block
   * _<_ or _>_: select the enclosing <> block
   * _"_: select the enclosing double quoted string
   * _'_: select the enclosing single quoted string
   * _w_: select the whole word
   * _W_: select the whole WORD
  
  Registers
  ---------
  