On Thu, Mar 31 2022, Shaoxuan Yuan wrote:

+static int check_dir_in_index(const char *dir)
+{
+	int ret = 0;
+	int length = sizeof(dir) + 1;
+	char *substr = malloc(length);
+
+	for (int i = 0; i < the_index.cache_nr; i++) {

See https://lore.kernel.org/git/xmqqy20r3rv7.fsf@gitster.g/ (local) for how
we're not quite using this syntax yet.

This should also be "unsigned int" to go with the "cache_nr" member.

+		memcpy(substr, the_index.cache[i]->name, length);
+		memset(substr + length - 1, 0, 1);
+
+		if (strcmp(dir, substr) == 0) {

Style: don't compare against == 0, or == NULL, use !, see CodingGuidelines.

+			else if (check_dir_in_index(src_w_slash) &&
+			!path_in_sparse_checkout(src_w_slash, &the_index)) {

Funny indentation, the ! should be aligned with "(".

-				modes[i] = WORKING_DIRECTORY;
+				if (!modes[i])
+					modes[i] = WORKING_DIRECTORY;

This works, but assuming things about enum values (even if 0) always
seems a bit nasty, can this be a comparison to BOTH instead of !? May or
may not be better...

But then again we do xcalloc() to allocate it, so we assume that
already, nevermind... :)

(there were also indentation issues below)