anchor.diff:  
   == Value expansions
   
  -Expansions with the type `val` can be used in various places, depending on the
  -specific value.
  -
  -The following expansions are supported:
  +Expansions with the type `val` give access to Kakoune internal data that is
  +not stored in an option or a register. Some value expansions can only be used
  +in certain contexts, like `%val{hook_param}` that expands to the parameter
  +string of the currently-executing hook, and is not available outside a hook.
  +
  +The following expansions are supported (with required context _in italics_):
   
   *%val{buffile}*::
       _in buffer scope_ +
  
positive.code:      expands to argument number _n_ of the current command
  
  *%arg{@}*::
      expands to all the arguments of the current command, individually quoted
  
  == Option expansions
  
  
negative.code: `{}` are most common. For example, the command `echo %val{session}` will
  echo the ID of the current Kakoune session.
  
  Expansions are processed when unquoted and anywhere inside double-quoted
  strings, but not inside unquoted words, inside single-quoted strings, or
  inside %-strings or other expansions. So:
  
  * `echo %val{session}` echoes the current session ID
  
  