Adding cancel link/button to node edit forms in 6.x

There's been talk of adding a Cancel link or button to the node edit form in 7.x, and there's some enthusiasm for doing the same thing in 6.x

How should this be handled? A patch against node.module in 6.x-dev? A little module? A snippet?

(See the discussion of doing this in 7.x to see why it's supposed to be a link, not a button.)

Also, there's some debate about where the Cancel link should take you—to the node that you're editing or back to the page you were on before (when that's different)? Maybe we could use JavaScript to go back to the previous page in the browser history, and default to the node view when JS is disabled?