ref-filter: fix memory leak in `free_array_item()`

We treat the `value` pointer as a pointer to a struct and free its `s`
field. But `value` is in fact an array of structs. As a result, we only
free the first `s` out of `used_atom_cnt`-many and leak the rest. Make
sure we free all items in `value`.

In the caller, `ref_array_clear()`, this means we need to be careful not
to zero `used_atom_cnt` until after we've called `free_array_item()`. We
could move just a single line, but let's keep related things close
together instead, by first handling `array`, then `used_atom`.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

ref-filter.c

@@ -2105,7 +2105,9 @@ static void free_array_item(struct ref_array_item *item)
 {
 	free((char *)item->symref);
 	if (item->value) {
-		free((char *)item->value->s);
+		int i;
+		for (i = 0; i < used_atom_cnt; i++)
+			free((char *)item->value[i].s);
 		free(item->value);
 	}
 	free(item);
@@ -2116,14 +2118,16 @@ void ref_array_clear(struct ref_array *array)
 {
 	int i;
 
-	for (i = 0; i < used_atom_cnt; i++)
-		free((char *)used_atom[i].name);
-	FREE_AND_NULL(used_atom);
-	used_atom_cnt = 0;
 	for (i = 0; i < array->nr; i++)
 		free_array_item(array->items[i]);
 	FREE_AND_NULL(array->items);
 	array->nr = array->alloc = 0;
+
+	for (i = 0; i < used_atom_cnt; i++)
+		free((char *)used_atom[i].name);
+	FREE_AND_NULL(used_atom);
+	used_atom_cnt = 0;
+
 	if (ref_to_worktree_map.worktrees) {
 		hashmap_free(&(ref_to_worktree_map.map), 1);
 		free_worktrees(ref_to_worktree_map.worktrees);