elisp-showdoc.el

(defun elisp-showdoc (f)
  (interactive (list (thing-at-point 'symbol t)))
  (message
   "%s"
   (let* ((doc-list      (split-string (documentation (intern f)) "\n"))
          (number-lines  (min (- (floor (* max-mini-window-height (frame-height))) 2)
                              (- (length doc-list) 2)))
          (subset        (concatenate 'list
                                      (last doc-list)
                                      '("")
                                      (subseq doc-list 0 number-lines)))
          (pruned-subset (if (string-equal (car (last subset)) "")
                             (butlast subset)
                             subset)))
     (mapconcat #'identity pruned-subset "\n"))))