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.
이러한 오류가 뜨는 이유 : github에서 레포지토리를 생성할 때, README.md 파일을 생성했기 때문이다.
오류 해결 : git push -f origin master 라고 치면 잘 올라간다.