Fix GMane's Archived-At header

(defun tess-mangle-gmane-archival-gnus-data (link)
  "Mangle the `gnus-data' property value LINK.
Specifically, change the archival URL from permalink.gmane.org (Gmane's
blog-like interface) to article.gmane.org (Gmane's newslike interface)."
  (let ((original-date (get-text-property 5 'original-date link))
        (face (get-text-property 5 'face link)))
    (propertize (replace-regexp-in-string "permalink.gmane.org"
                                          "article.gmane.org"
                                          (substring-no-properties link))
                'face face 'original-date original-date)))

(defun tess-mangle-gmane-archival-header ()                                          
  "Mangle Gmane's Archived-At header to be more useful.                              
Specifically, change the archival URL from permalink.gmane.org (Gmane's              
blog-like interface) to article.gmane.org (Gmane's newslike interface)."             
  (gnus-with-article-headers                                                         
   (when (gnus-article-goto-header "Archived-At")                                    
     (save-excursion                                                                 
       (alter-text-property (+ 2 (point)) (1- (line-end-position))                   
                            'gnus-data                                               
                            'tess-mangle-gmane-archival-gnus-data))                  
     (when (re-search-forward "permalink.gmane.org"                                  
                              (line-end-position) t)                                 
       (replace-match (propertize "article.gmane.org"                                
                                  'face 'gnus-header-content))))))                   
                                                                                     
(add-hook 'gnus-article-prepare-hook 'tess-mangle-gmane-archival-header)