sparse-checkout: fix cone mode behavior mismatch

The intention of the special "cone mode" in the sparse-checkout
feature is to always match the same patterns that are matched by the
same sparse-checkout file as when cone mode is disabled.

When a file path is given to "git sparse-checkout set" in cone mode,
then the cone mode improperly matches the file as a recursive path.
When setting the skip-worktree bits, files were not expecting the
MATCHED_RECURSIVE response, and hence these were left out of the
matched cone.

Fix this bug by checking for MATCHED_RECURSIVE in addition to MATCHED
and add a test that prevents regression.

Reported-by: Finn Bryant <finnbryant@gmail.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1091-sparse-checkout-builtin.sh

@@ -305,6 +305,18 @@ test_expect_success 'different sparse-checkouts with worktrees' '
 	check_files worktree a deep
 '
 
+test_expect_success 'set using filename keeps file on-disk' '
+	git -C repo sparse-checkout set a deep &&
+	cat >expect <<-\EOF &&
+	/*
+	!/*/
+	/a/
+	/deep/
+	EOF
+	test_cmp expect repo/.git/info/sparse-checkout &&
+	check_files repo a deep
+'
+
 check_read_tree_errors () {
 	REPO=$1
 	FILES=$2

unpack-trees.c

@@ -1416,7 +1416,7 @@ static int clear_ce_flags_1(struct index_state *istate,
 						name, &dtype, pl, istate);
 		if (ret == UNDECIDED)
 			ret = default_match;
-		if (ret == MATCHED)
+		if (ret == MATCHED || ret == MATCHED_RECURSIVE)
 			ce->ce_flags &= ~clear_mask;
 		cache++;
 		progress_nr++;