Untabify

untabify.el

;; I don't want to introduce tabs in my code; but I don't want to break Makefiles,
;; or to introduce diffs in third party code.

;; Here is my solution:
(defun my-untabify-buffer ()
  "Untabify the current buffer, unless `my-untabify-this-buffer' is nil."
  (and my-untabify-this-buffer (untabify (point-min) (point-max))))

(define-minor-mode my-untabify-mode
  "Untabify buffer on save." nil " untab" nil
  (if my-untabify-mode
      (progn
        (make-variable-buffer-local 'my-untabify-this-buffer)
        (setq my-untabify-this-buffer (not (derived-mode-p 'makefile-mode)))
        (add-hook 'before-save-hook 'my-untabify-buffer nil t))
    (progn
      (kill-local-variable 'my-untabify-this-buffer)
      (remove-hook 'before-save-hook 'my-untabify-buffer t))))