I\'m working on a team with a few developers using git on BitBucket. We are all working on a dev branch, not pushing to master until a release.
Well actually github is much simpler than we think and absolutely it happens whenever we try to push even after we explicitly inserted some files in our git repository so, in order to fix the issue simply try..
: git pull
and then..
: git push
Note: if you accidently stuck in vim editor after pulling your repository than don't worry just close vim editor and try push :)