This cleans up diff_scoreopt_parse() function that is used to
parse the fractional notation -B, -C and -M option takes.  The
callers are modified to check for errors and complain.  Earlier
they silently ignored malformed input and falled back on the
default.
Signed-off-by: NJunio C Hamano <junkio@cox.net>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>