bisect: don't mix option parsing and non-trivial code

bisect: don't mix option parsing and non-trivial code

As-is, the revisions that appear on the command-line are processed in
order. This would mix badly with code that changes the configuration
(e.g. change $TERM_GOOD and $TERM_BAD) while processing the options.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>