anchor.diff:                ;; formatted
                 (unless (empty? curr)
                   (push curr (options [files])))
  -            (let ((indent-pair
  +            (let ((output-pair
  +                   (if (or (and (not (matches-opt? "-output" prev))
  +                                (matches-opt? "-output" curr))
  +                           (and (not (matches-opt? "-o" prev))
  +                                (matches-opt? "-o" curr)))
  +                       ;; The "-backup-dir" string is at the end of the arg list
  +                       (list curr "")
  +                     (if (or (matches-opt? "-o" prev)
  +                             (matches-opt? "-output" prev))
  +                         (list prev curr)
  +                       (list "" ""))))
  +                  (indent-pair
                      (if (or (and (not (matches-opt? "-default-indent" prev))
                                   (matches-opt? "-default-indent" curr))
                              (and (not (matches-opt? "-di" prev))
                                   (matches-opt? "-di" curr)))
  -                       ;; The "--backup-dir" string is at the end of the arg list
  +                       ;; The "-backup-dir" string is at the end of the arg list
                          (list curr "")
                        (if (or (matches-opt? "-di" prev)
                                (matches-opt? "-default-indent" prev))
  
positive.code:                       (setq (options [backup-dir]) (backup-dir-pair 1))
                      (setq (options [backup-dir]) (join (rest lst) "=")))))
                (cond
                 ((matches-opt? "-nc" curr) (setq (options [compact]) nil))
                 ((matches-opt? "-no-compact" curr) (setq (options [compact]) nil))
                 ((matches-opt? "-nb" curr) (setq (options [backup]) nil))
  
negative.code:          (option-arg?
            (lambda (arg)
              (or
               (matches-opt? "-o" arg)
               (matches-opt? "-output" arg)
               (matches-opt? "-dialect" arg)
               (matches-opt? "-bd" arg)
               (matches-opt? "-backup-dir" arg)
  