Here’s how I got rjsilk/vagrant-github-pages to work to publish this site back in 2015:

#write to synced folder /vagrant/files/.gitconfig
cat > /vagrant/files/.gitconfig
  name = Richard Chen
  email = 
  ui = auto

#build the environment
sudo apt-get update && sudo apt-get -y install build-essential git curl nodejs
gpg --keyserver hkp:// --recv-keys D39DC0E3
curl -sSL | bash -s stable --rails
source /usr/local/rvm/scripts/rvm
sudo gem install github-pages --no-ri --no-rdoc

#customize for user, inside vagrant ssh
cd /vagrant
git submodule add
cat > ~/.bash_profile
cp /vagrant/files/.gitconfig /home/vagrant/.gitconfig
cd /vagrant/

#start working

I’ve since moved to Docker.