To deploy a site to GitHub Pages, you simple need to create a branch named
gh-pages that points to the commit that would like to deploy. For example:
$ git checkout master
$ git checkout -b gh-pages
$ git push -u origin gh-pages
Or for an existing gh-pages branch:
$ git checkout gh-pages
$ git merge master
$ git push
It is imperative that there is a file named index.html in the gh-pages
branch so that GitHub Pages has a file to serve.