Function set_default

src/Config.cpp:133–135

template<class T>
static void set_default(config_tree &tree, bool &modified, const config_tree::key_type &key, T value) {
    if (!tree.get_child_optional(key)) tree.put(key, value), modified = true;
}

static bool set_defaults(config_tree &tree) {
    bool modified = false;