anchor.diff:      is not a valid regex
   
   *coord*::
  -    a line, column pair (separated by comma)
  +    a line, column pair (separated by a comma)
   
   *<type>-list*::
       a list, elements are separated by a colon (:) if an element needs
  -    to contain a colon, it can be escaped with a backslash
  +    to contain a colon, it can be escaped with a backslash.
  +    `set -add` appends the new element to the list
   
   *range-specs*::
       a `:` separated list of a pair of a buffer range (`<begin
  
positive.code: Options can be modified using the `set-option` command:
  
  ---------------------------------
  set-option <scope> <name> <value>
  ---------------------------------
  
  <scope> can be *global*, *buffer*, *window* or *current* (See
  <<scopes#,`:doc scopes`>>). *current* relate to the narrowest scope in
  which the option is already set.
  
  [[unset-option]]
  Options values can be unset in a specific scope with the `unset-option`
  
negative.code: 
  *flags(value1|value2|...)*::
      a set of flags, taking a combination of the given values joined by a
      '|' character.
      `set -add` adds the new flag to the combination
  
  *<type>-to-<type>-map*::
      a `:` separated list of `key=value` pairs.
      `set -add` adds the new pair to the hashmap or replace an already
      existing key.
  
  == Builtin options
  
  