blame: pay attention to --no-follow

blame: pay attention to --no-follow

If you know your history did not have renames, or if you care only
about the history after a large rename that happened some time ago,
"git blame --no-follow $path" is a way to tell the command not to
bother about renames.

When you use -C, the lines that came from the renamed file will
still be found without the whole-file rename detection, so it is not
all that interesting either way, though.

Signed-off-by: Junio C Hamano <gitster@pobox.com>