Inverse of M-q, an unfill-paragraph-function

Question

Is there an inverse for M-q, some kind of unfill-paragraph-function?

If I have undo data, then it\'s of course easy. What I am asking for is

Answer 1

I was first using @sanityinc's solution for a while until I came accross Stefan Monnier's Unfill Paragraph in EmacsWiki. It seems more robust

;;; Stefan Monnier . It is the opposite of fill-paragraph    
(defun unfill-paragraph (&optional region)
  "Takes a multi-line paragraph and makes it into a single line of text."
  (interactive (progn (barf-if-buffer-read-only) '(t)))
  (let ((fill-column (point-max))
        ;; This would override `fill-column' if it's an integer.
        (emacs-lisp-docstring-fill-column t))
    (fill-paragraph nil region)))

;; Handy key definition
(define-key global-map "\M-Q" 'unfill-paragraph)

The M-Q key binding makes the command so much easier.