anchor.diff:                 ;; First return value is the cons cell for the pair,
                  ;; second is the list as a whole, which is now headed by this pair.
                  (values pair pair)))
  +           (insert-at-end (head &aux (rest (cdr head)))
  +             (if (not rest)
  +                 (insert-after head)
  +                 (insert-at-end (cdr rest))))
              (insert-after (tail)
                ;; A picture: list is (#<FIELD A> a-val #<FIELD C> c-val #<FIELD D> d-val ...)
                ;;                                ^--- TAIL points here
  
positive.code:                           (insert-in (cdr rest))))))))
      (if (not field-list)
          (insert-at-front)
          (let* ((field (car field-list))
                 (index (field-index field)))
            (cond ((i> field-number index) ; greater than any field number seen thus far
                   (insert-at-front))
                  ((i= field-number index) ; a field number which has been seen before
                   (values field-list field-list))
                  (t                       ; keep on looking
                   (insert-in (cdr field-list))))))))
  
  (defun deserialize-structure-object (message buffer index limit end-tag class)
    "Deserialize a message.
  
negative.code:     (deserialize-structure-object
       msg-desc buffer start end end-tag class)))
  
  (defstruct (field (:constructor make-field (index offset bool-index oneof-p initarg complex-field))
                    (:print-object
                     (lambda (self stream)
                       (format stream "#<~D~S>" (field-index self) (field-initarg self)))))
    "Field metadata for a protocol buffer.
  Contains the INDEX of the field as according to protobuf, an internal
  OFFSET, the BOOL-NUMBER (for simple boolean fields), a flag ONEOF-P which indicates if the field
  is part of a oneof, the INITARG, the COMPLEX-FIELD datastructure.
  See field-descriptor for the distinction between index, offset, and bool-number."
    index
    offset
    bool-index
    oneof-p
    initarg
    complex-field)
  
  