You can setup git push to push to multiple repos.

git remote set-url --add origin ...

I use GitLab as the primary source, and mirror it to GitHub.

Or, I would have, if the builtin GitLab mirroring feature wasn't broken for pushing to GitHub.

I use multiple hosts to backup my repos: I host gitolite.org on a $5 VM and then have it configured to automatically push to gitlab and GitHub on every change.

My guess is some form of:

git checkout master

git pull github/master

git push gitlab/master

It's quite easy to set a git repo up to push to multiple upstreams. https://gist.github.com/bjmiller121/f93cd974ff709d2b968f also see https://stackoverflow.com/a/849960/308851