Odd "git diff" breakage

I hit this oddity when not remembering the right syntax for --color-words..

Try this (outside of a git repository):

   touch a b
   git diff -u --color=words a b

and watch it scroll (infinitely) printing out

   error: option `color' expects "always", "auto", or "never"

forever.

I haven't tried to root-cause it, since I'm supposed to be merging stuff..

                Linus