A small elisp snippet for automatic +x on scripts

my_auto-file-mode.el

  (defun my:auto-file-mode ()
    (when (save-excursion
	    (save-restriction
	      (widen)
	      (goto-char (point-min))
	      (save-match-data
		(looking-at "^#!"))))
      (let* ((cmode (file-modes buffer-file-name))
	     (nmode (logior cmode (lsh (logand cmode #o444) -2))))
	(when (not (= cmode nmode))
	  (message "Changing mode of script %s to %o"
		   buffer-file-name nmode)
	  (set-file-modes buffer-file-name nmode)))))

  (add-hook 'after-save-hook 'my:auto-file-mode)