Advice shell-command and friends to use /bin/bash

foo.el

(loop
 for f  in 
 '(shell-command  shell-command-on-region shell-command-as-string)
 do
 (eval
  `(defadvice  ,f (around fix-shell pre act comp)
     "Use a sane shell"
     (let ((shell-file-name "/bin/bash"))
       ad-do-it))))