unpack-trees: fix sparse directory recursion check

Ensure 'is_sparse_directory_entry()' receives a valid 'name_entry *' if one
exists in the list of tree(s) being unpacked in 'unpack_callback()'.

Currently, 'is_sparse_directory_entry()' is called with the first
'name_entry' in the 'names' list of entries on 'unpack_callback()'. However,
this entry may be empty even when other elements of 'names' are not (such as
when switching from an orphan branch back to a "normal" branch). As a
result, 'is_sparse_directory_entry()' could incorrectly indicate that a
sparse directory is *not* actually sparse because the name of the index
entry does not match the (empty) 'name_entry' path.

Fix the issue by using the existing 'name_entry *p' value in
'unpack_callback()', which points to the first non-empty entry in 'names'.
Because 'p' is 'const', also update 'is_sparse_directory_entry()'s
'name_entry *' argument to be 'const'.

Finally, add a regression test case.

Reported-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 5dced39889..16abac5d2b 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -380,6 +380,15 @@ test_expect_success 'checkout with modified sparse directory' '
 	test_all_match git checkout base
 '
 
+test_expect_success 'checkout orphan then non-orphan' '
+	init_repos &&
+
+	test_all_match git checkout --orphan test-orphan &&
+	test_all_match git status --porcelain=v2 &&
+	test_all_match git checkout base &&
+	test_all_match git status --porcelain=v2
+'
+
 test_expect_success 'add outside sparse cone' '
 	init_repos &&