fixup! read-cache: add test for post-indexchanged hook

Ben implemented a short-cut for `git checkout -b` which avoids writing
the index. Therefore, no hook would be called in that case. Let's force
it do be called by using `-B` instead of `-b`.

Author: dscho

t/t7113-post-index-changed-hook.sh

@@ -96,7 +96,7 @@ test_expect_success 'test checkout and reset trigger the hook' '
 	git reset --hard &&
 	test_path_is_file testsuccess && rm -f testsuccess &&
 	test_path_is_missing testfailure &&
-	git checkout -b test &&
+	git checkout -B test &&
 	test_path_is_file testsuccess && rm -f testsuccess &&
 	test_path_is_missing testfailure
 '