Bisect visualize: use "for-each-ref" to list all good refs.

In bisect_visualize, "cd $GIT_DIR/refs && echo bisect/good-*" was
still used instead of "git for-each-ref". This patch fix it.

We now pass "refs/bisect/bad" and "--not refs/bisect/good-<rev>"
instead of "bisect/bad" and "--not bisect/good-<rev>" to gitk,
but it seems to work.

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

git-bisect.sh

@@ -324,8 +324,8 @@ bisect_next() {
 
 bisect_visualize() {
 	bisect_next_check fail
-	not=`cd "$GIT_DIR/refs" && echo bisect/good-*`
-	eval gitk bisect/bad --not $not -- $(cat "$GIT_DIR/BISECT_NAMES")
+	not=$(git for-each-ref --format='%(refname)' "refs/bisect/good-*")
+	eval gitk refs/bisect/bad --not $not -- $(cat "$GIT_DIR/BISECT_NAMES")
 }
 
 bisect_reset() {