当我们在提交代码到Github时（执行git push命令时），可能会不出现密码弹窗，直接提示以下问题：
remote: Password authentication is temporarily disabled as part of a brownout. Please use a personal access token instead.
remote: Please see https://github.blog/2020-07-30-token-authentication-requirements-for-api-and-git-operations/ for more information.
fatal: unable to access 'https://github.com/xxx/xxx.git/': The requested URL returned error: 403
这个时候其实是由于我们设置了credential.helper，只需要执行如下命令即可解决此问题：
git config --system --unset credential.helper
