name-hash: don't add sparse directories in threaded lazy init

Ensure that logic added in 5f11669 (name-hash: don't add directories
to name_hash, 2021-04-12) also applies in multithreaded hashtable init
path.

As per the original single-threaded change above: sparse directory entries
represent a directory that is outside the sparse-checkout definition.
These are not paths to blobs, so should not be added to the name_hash
table. Instead, they should be added to the directory hashtable when
'ignore_case' is true.

Add a condition to avoid placing sparse directories into the name_hash
hashtable. This avoids filling the table with extra entries that will
never be queried.

Signed-off-by: Alex Mironov <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: alexandrfox

name-hash.c

@@ -492,8 +492,10 @@ static void *lazy_name_thread_proc(void *_data)
 	for (k = 0; k < d->istate->cache_nr; k++) {
 		struct cache_entry *ce_k = d->istate->cache[k];
 		ce_k->ce_flags |= CE_HASHED;
-		hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);
-		hashmap_add(&d->istate->name_hash, &ce_k->ent);
+		if (!S_ISSPARSEDIR(ce_k->ce_mode)) {
+			hashmap_entry_init(&ce_k->ent, d->lazy_entries[k].hash_name);
+			hashmap_add(&d->istate->name_hash, &ce_k->ent);
+		}
 	}
 
 	return NULL;