title: Emacs Lisp function to toggle variable 'tab-width' between 4 & 8
body: <p>The source tree that I work on has files indented with different tab values, (not to mention spaces) and the best I can do is to set emacs to use the style found in the region of code I am modifying. Instead of doing M-x set-variable tab-width to 4 or 8, a key binding to toggle the tab-width among these two value would help immensely.</p>
  
  <p>Thanks.</p>