[bug-diffutils] bug#17075: diff - - exits immediately

[Karl Berry]

With diff 3.3, running
  diff - -
exits immediately, and successfully, for me.  (Compiled from the original
GNU source, running on CentOS 6.5.)

It seems like it should either read stdin twice (probably too much
trouble), or read stdin once and then abort when it can't be read again,
or just abort immediately.  Or something, just not success.

FWIW ...

karl