把项目备份到GitHub已存在的仓库

git init
git add read.txt（需要push的文件。或这使用）
git commit -m '描述信息'
git remote add origin url  （可以从GitHub直接赋值）

如果出现

To https://github.com/SomeoneCute/learngit1.git

 ! [rejected]        master -> master (fetch first)
error: failed to push some refs to 'https://github.com/SomeoneCute/learngit1.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.

hint: See the 'Note about fast-forwards' in 'git push --help' for details.

需要先pull下来：
git pull origin 分支名（比较多的直接使用master）

再push：

git push origin 分支名

（或者切换分支后再push：git checkout 分支名）