how to make your own forms indent properly in emacs with clojure-mode

emagic.clj

(defn pumpkin [op & args]
  (apply op args))

(pumpkin +
         1
         2
         3)

;; in emacs do:
;;   M-x eval-expression
;;   (define-clojure-indent (pumpkin 'defun))

(pumpkin +
  1
  2
  3)