title: emacs: is before-save-hook a local variable?
body: <p>how would I figure this out?  </p>
  
  <p>I added <code>delete-trailing-whitespace</code> to the <code>before-save-hook</code> in my <code>c-mode-common-hook</code>, but it looks like <code>delete-trailing-whitespace</code> is getting called for every file, not just buffers using c-mode and derivatives.  </p>
  
  <p>Can I make the <code>before-save-hook</code> buffer local?</p>