composer修改镜像出错

全局命令composer config -g repo.packagist 提示：composer config repo.packagist composer https://packagist.phpcomposer.com 修改镜像命令composer https://packagist.phpcomposer.com 提示： [Symfony\Component\Console\Exception\CommandNotFoundException]   There are no commands defined in the "https" namespace.   这两个怎么解决