bisect: parse revs before passing them to check_expected_revs()

bisect: parse revs before passing them to check_expected_revs()

When running for example "git bisect bad HEAD" or
"git bisect good master", the parameter passed to
"git bisect (bad|good)" has to be parsed into a
commit hash before checking if it is the expected
commit or not.

We could do that in is_expected_rev() or in
check_expected_revs(), but it is already done in
bisect_state(). Let's just store the hash values
that result from this parsing, and then reuse
them after all the parsing is done.

This way we can also use a for loop over these
values to call bisect_write() on them, instead of
using eval.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>