anchor.diff:  Getting these links to work using only Markdown will require added explicit
   reference link information that will be tied to the file _names_. Markdown-many,
   on the other hand, will automatically combine the link information and
  -process it automatically.
  +processes it automatically.
   "
     (let ((main-document (make-instance 'document))
   	(docs nil))
  
positive.code:        (starts-with url "mailto:")
         (starts-with url "file:"))))
   
  (defmethod transfer-link-info ((info extended-link-info)
  			       parent child destination)
    (declare (ignore parent child destination))
    (make-instance 'extended-link-info
  
negative.code:  :format :html)
  
  (defun transfer-document-data (parent child destination)
    (transfer-link-info parent child destination)
    (transfer-selected-properties 
     parent child 
     (set-difference (collect-keys (properties child))
  		   (list :footnote :style-sheet :style-sheets :title))))
  
  (defun transfer-selected-properties (parent child properties)
    (let ((*current-document* parent))
      (iterate-elements 
       properties
       (lambda (property)
         (when (item-at-1 (properties child) property)
  	 (setf (document-property property) 
  	       (first (item-at-1 (properties child) property))))))))
  
  (defun transfer-link-info (parent child destination)
    (let ((*current-document* parent))
      (iterate-key-value
       (link-info child)
       (lambda (id info)
         (setf (item-at (link-info parent) id)
  	     (transfer-1-link-info info parent child destination))))))
  
  (defgeneric transfer-1-link-info (info parent child destination))
  
  (defmethod transfer-1-link-info ((info link-info) parent child destination)
    (declare (ignore parent child))
    (make-instance 'link-info
                   :id (id info)
  		 :url (if (relative-url-p (url info))
  			  (format nil "~@[~a~]~@[.~a~]~a" 
  				  (pathname-name destination)
  				  (pathname-type destination)
  				  (url info))
  