list-objects-filter-options: create copy helper

As we add more embedded members with type 'struct
list_objects_filter_options', it will be important to easily perform a
deep copy across multiple such structs. Create
list_objects_filter_copy() to satisfy this need.

This method is recursive to match the recursive nature of the struct.

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

list-objects-filter-options.c

@@ -415,3 +415,22 @@ void partial_clone_get_default_filter_spec(
 					 &errbuf);
 	strbuf_release(&errbuf);
 }
+
+void list_objects_filter_copy(
+	struct list_objects_filter_options *dest,
+	const struct list_objects_filter_options *src)
+{
+	int i;
+	struct string_list_item *item;
+
+	/* Copy everything. We will overwrite the pointers shortly. */
+	memcpy(dest, src, sizeof(struct list_objects_filter_options));
+
+	string_list_init_dup(&dest->filter_spec);
+	for_each_string_list_item(item, &src->filter_spec)
+		string_list_append(&dest->filter_spec, item->string);
+
+	ALLOC_ARRAY(dest->sub, dest->sub_alloc);
+	for (i = 0; i < src->sub_nr; i++)
+		list_objects_filter_copy(&dest->sub[i], &src->sub[i]);
+}

list-objects-filter-options.h

@@ -132,4 +132,8 @@ void partial_clone_get_default_filter_spec(
 	struct list_objects_filter_options *filter_options,
 	const char *remote);
 
+void list_objects_filter_copy(
+	struct list_objects_filter_options *dest,
+	const struct list_objects_filter_options *src);
+
 #endif /* LIST_OBJECTS_FILTER_OPTIONS_H */