This doesn't actually work at all as post is the post *class* here and not an individual instance.

What you probably want is something closer to:
```lisp
(defmethod deploy :after (staging)
  ;; revision is currently passed into coleslaw and unused in the main function.
  ;; i'll probably stash it in a global variable *last-revision* in the near future
  (loop for (state file) in (get-updated-files *last-revision*)
      when (and (string= "A" state) (string= "post" (pathname-type file))) ;; New blog post was added.
      do (tweet-new-post file)))

;; I'll also probably need to add some machinery that tracks the original file path or hash of posts to CONTENT.
;; And provide a lookup based on that.
(defun tweet-new-post (post)
  "Retrieve most recent post from in memory DB and publish it."
  (let ((post (find-content-by-path file)))
    (chirp:statuses/update (%format-post post)))
```