anchor.diff:  ...will find none of Kakoune's special environment variables, but:
   
   ----
  -echo %sh{ env | grep ^kak_ # $kak_session }
  -----
  -
  -...will find the `$kak_session` variable because it was mentioned inside the
  -shell script, even just in a comment.
  +echo %sh{ env | grep ^kak_ # kak_session }
  +----
  +
  +...will find the `$kak_session` variable because it was mentioned by name
  +in a comment, even though it wasn't directly used.
   
   TIP: These environment variables are also available in other contexts where
   Kakoune uses a shell command, such as the `|`, `!` or `$` normal mode commands
  
positive.code: 
  * `echo "x%val{session}x"` echoes the current session ID, surrounded by `x`
  
  * `echo %{x%val{session}x}"` echoes the current session ID, surrounded by `x`
  
  * `echo %sh{ echo %val{session} }"` echoes the literal text `%val{session}`
  
  When processing an expansion, Kakoune ensures the result is properly quoted so
  that any special characters do not interfere with the rest of the command. If
  an expansion expands to multiple values, each value is individually quoted.
  
  == Argument expansions
  
  
negative.code:      expands to argument number _n_ of the current command
  
  *%arg{@}*::
      expands to all the arguments of the current command, as individual words
  
  == Option expansions
  
  