[git] ! [rejected] master -> master (non-fast-forward)

root@hct1[~/linux-work-env]{01:32}(0)# git push -u origin master
Password:
To https://peicheng@github.com/peicheng/linux-work-env.git
! [rejected] master -> master (non-fast-forward)
error: failed to push some refs to 'https://peicheng@github.com/peicheng/linux-work-env.git'
To prevent you from losing history, non-fast-forward updates were rejected
Merge the remote changes before pushing again. See the 'Note about
fast-forwards' section of 'git push --help' for details.

$ git pull
$ git push -u origin master
or 
$ git fetch
$ git merge 
$ git push -u origin master