anchor.diff:      (let* ((instance (make-instance file-info-class))
              (key (plist-key instance))
              (file-info-plist (getf plist key)))
  +      (unless file-info-plist
  +        (error "Missing client-info data for ~S" key))
         (destructuring-bind (&key url size md5 sha256 &allow-other-keys)
             file-info-plist
  +        (unless (and url size md5 sha256)
  +          (error "Missing client-info data for ~S" key))
           (reinitialize-instance instance
                                  :plist file-info-plist
                                  :url url
  
positive.code:   (:default-initargs
     :plist-key :client-tar
     :name "quicklisp.tar"))
  
  (defclass client-info ()
    ((setup-info
  
negative.code: 
  ;;; Information for checking the validity of files fetched for
  ;;; installing/updating the client code.
  
  (defclass client-file-info ()
    ((plist-key
  