how to open *.info file in emacs in info mode?

emacs

Solution

Plain (info `file-name') opens file in info mode. (info) probably does something besides just setting Info-mode. So I would use something like this:

(defun info-mode ()
  (interactive)
  (let ((file-name (buffer-file-name)))
    (kill-buffer (current-buffer))
    (info file-name)))
(add-to-list 'auto-mode-alist '("\\.info\\'" . info-mode))

Problem

`C-x C-f blah.info` opens the file in fundametal mode. I used `apropos` and found `Info-mode` which I thought might change from fundamental mode into Info mode, but that throws a lisp error. How can I open a external/thirdparty *.info file in emacs so that I get the same bells and whistles as when I'm looking at `M-x info` (`n` for next, `u` for up, hyperlinks, etc..)? I'm sure this is obvious, but I can't figure it out.

Original source