anchor.diff:  returned file-path is relative to the link, not
   *DEFAULT-FILE-PATH-DEFAULTS*.
   
  -Signals an error if PATHSPEC is wild, or does not designate a
  -symbolic link."
  +Signals an error if PATHSPEC is not a symbolic link."
     ;; Note: the previous version tried much harder to provide a buffer
     ;; big enough to fit the link's name.  OTOH, NIX:READLINK stack
     ;; allocates on most lisps.
  
positive.code: *DEFAULT-FILE-PATH-DEFAULTS*.
  
  SETF CURRENT-DIRECTORY changes the operating system's current
  directory to the PATHSPEC.  An error is signalled if the PATHSPEC
  is wild or does not designate a directory."
    (let ((cwd (%sys-getcwd)))
      (if cwd
          (parse-file-path cwd :expand-user nil)
  
negative.code: :GROUP-READ, :GROUP-WRITE, :GROUP-EXEC, :OTHER-READ, :OTHER-WRITE,
  :OTHER-EXEC, :SET-USER-ID, :SET-GROUP-ID, and :STICKY.
  
  Both signal an error if PATHSPEC doesn't designate an existing file."
    (let ((mode (stat-mode (%sys-stat (file-path-namestring pathspec)))))
      (loop :for (name . value) :in +permissions+
            :when (plusp (logand mode value))
  