diff_setup() used to initialize output_format to DIFF_FORMAT_RAW. Now
the default is 0 (no output) so don't compare against DIFF_FORMAT_RAW to
see if any diff format command line flags were given.
Signed-off-by: Timo Hirvonen <tihirvon@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>