t7012: Mark missing tests as TODO

Currently, there are 6 tests which are not even written but are
'test_expect_failure message false'.
Do not abuse test_expect_failure as a to do marker, but mark them as
'#TODO' instead.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Acked-by: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7012-skip-worktree-writing.sh

@@ -136,11 +136,11 @@ test_expect_success 'git-clean, dirty case' '
 	test_cmp expected result
 '
 
-test_expect_failure 'git-apply adds file' false
-test_expect_failure 'git-apply updates file' false
-test_expect_failure 'git-apply removes file' false
-test_expect_failure 'git-mv to skip-worktree' false
-test_expect_failure 'git-mv from skip-worktree' false
-test_expect_failure 'git-checkout' false
+#TODO test_expect_failure 'git-apply adds file' false
+#TODO test_expect_failure 'git-apply updates file' false
+#TODO test_expect_failure 'git-apply removes file' false
+#TODO test_expect_failure 'git-mv to skip-worktree' false
+#TODO test_expect_failure 'git-mv from skip-worktree' false
+#TODO test_expect_failure 'git-checkout' false
 
 test_done