t1092: document bad sparse-checkout behavior

There are several situations where a repository with sparse-checkout
enabled will act differently than a normal repository, and in ways that
are not intentional. The test t1092-sparse-checkout-compatibility.sh
documents some of these deviations, but a casual reader might think
these are intentional behavior changes.

Add comments on these tests that make it clear that these behaviors
should be updated. Using 'NEEDSWORK' helps contributors find that these
are potential areas for improvement.

Helped-by: Elijah Newren <[email protected]>
Reviewed-by: Elijah Newren <[email protected]>
Signed-off-by: Derrick Stolee <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

t/t1092-sparse-checkout-compatibility.sh

@@ -392,8 +392,8 @@ test_expect_failure 'blame with pathspec outside sparse definition' '
 	test_all_match git blame deep/deeper2/deepest/a
 '
 
-# TODO: reset currently does not behave as expected when in a
-# sparse-checkout.
+# NEEDSWORK: a sparse-checkout behaves differently from a full checkout
+# in this scenario, but it shouldn't.
 test_expect_failure 'checkout and reset (mixed)' '
 	init_repos &&
 
@@ -403,8 +403,8 @@ test_expect_failure 'checkout and reset (mixed)' '
 	test_all_match git reset update-folder2
 '
 
-# Ensure that sparse-index behaves identically to
-# sparse-checkout with a full index.
+# NEEDSWORK: a sparse-checkout behaves differently from a full checkout
+# in this scenario, but it shouldn't.
 test_expect_success 'checkout and reset (mixed) [sparse]' '
 	init_repos &&
 
@@ -524,6 +524,8 @@ test_expect_success 'sparse-index is not expanded' '
 	test_region ! index ensure_full_index trace2.txt
 '
 
+# NEEDSWORK: a sparse-checkout behaves differently from a full checkout
+# in this scenario, but it shouldn't.
 test_expect_success 'reset mixed and checkout orphan' '
 	init_repos &&