sparse checkout: show error messages when worktree shaping fails

verify_* functions can queue errors up and to be printed later at
label return_failed. In case of errors, do not go to label "done"
directly because all queued messages would be dropped on the floor.

Found-by: Joshua Jensen <jjensen@workspacewhiz.com>
Tracked-down-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/t/t1011-read-tree-sparse-checkout.sh b/t/t1011-read-tree-sparse-checkout.sh
index 018c354..efcd8ab 100755
--- a/t/t1011-read-tree-sparse-checkout.sh
+++ b/t/t1011-read-tree-sparse-checkout.sh
@@ -234,4 +234,19 @@
 	test_cmp empty result
 '
 
+test_expect_success 'print errors when failed to update worktree' '
+	echo sub >.git/info/sparse-checkout &&
+	git checkout -f init &&
+	mkdir sub &&
+	touch sub/added sub/addedtoo &&
+	test_must_fail git checkout top 2>actual &&
+	cat >expected <<\EOF &&
+error: The following untracked working tree files would be overwritten by checkout:
+	sub/added
+	sub/addedtoo
+Please move or remove them before you can switch branches.
+EOF
+	test_cmp expected actual
+'
+
 test_done