推送到Git返回致命错误代码403

我想将README.md推送到Github.
使用Ubuntu 14.04LTS
因此，我按以下步骤进行操作.

I want to push README.md to Github.
Using Ubuntu 14.04LTS
So, I commit in the following steps.

echo "# test" >> README.md
git init
git add README.md
git commit -m "first commit"
git remote add origin https://github.com/user/repo.git
git push -u origin master

但是，发生以下错误.

error: The requested URL returned error: 403 Forbidden while accessing https://github.com/user/repo.git/info/refs

fatal: HTTP request failed

我知道可以通过这种方式解决此错误

I know solve this error this way

git remote set-url origin https://username@github.com/user/repo.git

这样，我必须输入密码.

In this way , I must enter password.

$ git push origin master
Password: 

但是我不想输入密码.

我已经检查过了，但是还没有解决.
推送到Git返回错误代码403致命:HTTP请求失败

I have checked this, but I don't solved.
Pushing to Git returning Error Code 403 fatal: HTTP request failed

请告诉我如何在没有密码的情况下进行推送.

Please tell me how to push without password.