git push 错误

$ git push -u origin master
error: src refspec master does not match any.
error: failed to push some refs to 'https://github.com/g2k/cpp-demo.git'

或者在QT creator push 错误
warning: push.default is unset; its implicit value has changed in
Git 2.0 from 'matching' to 'simple'. To squelch this message
and maintain the traditional behavior, use:

git config --global push.default matching

To squelch this message and adopt the new behavior now, use:

git config --global push.default simple

When push.default is set to 'matching', git will push local branches
to the remote branches that already exist with the same name.

Since Git 2.0, Git defaults to the more conservative 'simple'
behavior, which only pushes the current branch to the corresponding
remote branch that 'git pull' uses to update the current branch.

See 'git help config' and search for 'push.default' for further information.
(the 'simple' mode was introduced in Git 1.7.11. Use the similar mode
'current' instead of 'simple' if you sometimes use older versions of Git)

fatal: The current branch master has no upstream branch.
To push the current branch and set the remote as upstream, use

git push --set-upstream origin master

命令'C:\Program Files (x86)\Git\bin\git.exe'终止，退出代码128。

解决方法：

echo "# cpp-demo" >> README.md
git init
git add README.md
git commit -m "first commit"
git remote add origin https://github.com/g2k/cpp-demo.git
git push -u origin master