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.
dev
master
The error possibly comes because of the different structure of the code that you are committing and that present on GitHub. You may refer to: How to deal with "refusing to merge unrelated histories" error:
$ git pull --allow-unrelated-histories $ git push -f origin master