anchor.diff:  are exclusively available to built-in options.
   
   *int*::
  -    an integer number
  +    an integer number.
  +    `set -add` performs a math addition
   
   *bool*::
       a boolean value, yes/true or no/false
  
positive.code: 
  *flags(value1|value2|...)*::
      a set of flags, taking a combination of the given values joined by a
      '|' character
  
  == Builtin options
  
  
negative.code:     an option of this type, its lines gets updated according to all the
      buffer modifications that happened since its timestamp.
      See <<highlighters#specs-highlighters,`:doc highlighters specs-highlighters`>>)
      `set -add` appends the new spec to the list
  
  *completions*::
      a `:` separated list of `<text>|<docstring>|<menu text>`
  