bisect: simplify calling visualizer using '--bisect' option

In commit ad3f9a7 (Add '--bisect' revision machinery argument) the
'--bisect' option was added to easily pass bisection refs to
commands using the revision machinery.

So it is now shorter and safer to use the new '--bisect' revision
machinery option, than to compute the refs that we must pass.

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

git-bisect.sh

@@ -300,8 +300,7 @@ bisect_visualize() {
 		esac
 	fi
 
-	not=$(git for-each-ref --format='%(refname)' "refs/bisect/good-*")
+	eval '"$@"' --bisect -- $(cat "$GIT_DIR/BISECT_NAMES")
-	eval '"$@"' refs/bisect/bad --not $not -- $(cat "$GIT_DIR/BISECT_NAMES")
 }
 
 bisect_reset() {