(defun mm-display-patch-inline (handle)
  (let (text)
    (with-temp-buffer
      (mm-insert-part handle)
      (diff-mode)
      (font-lock-fontify-buffer)
      (setq text (buffer-string)))
    (mm-insert-inline handle text)))

(defun mm-display-elisp-inline (handle)
  (let (text)
    (with-temp-buffer
      (mm-insert-part handle)
      (emacs-lisp-mode)
      (font-lock-fontify-buffer)
      (setq text (buffer-string)))
    (mm-insert-inline handle text)))


(defun mm-add-new-type (type displayer test auto-display inlined attachment-override)
  (push (list type displayer test) mm-inline-media-tests)
  (if auto-display
      (push type mm-automatic-display))
  (if inlined
      (push type mm-inlined-types))
  (if attachment-override
      (push type mm-attachment-override-types)))

(eval-after-load "mm-decode"
  '(progn
     (mm-add-new-type "text/x-patch"        'mm-display-patch-inline '(fboundp 'diff-mode) t t t)
     (mm-add-new-type "application/x-patch" 'mm-display-patch-inline '(fboundp 'diff-mode) t t t)
     (mm-add-new-type "text/x-emacs-lisp"      'mm-display-elisp-inline 'identity t t t)
     (mm-add-new-type "application/emacs-lisp" 'mm-display-elisp-inline 'identity t t t)))