$ jekyll serve
From Stackoverflow Checkout your branch, where your build-source is located (master)
Remove all content of the _site directory: $ rm -r _site/*
Clone your repo's gh-pages branch into the _site directory:
$ git clone -b gh-pages git config remote.origin.url _site
Final steps: Just let jekyll build, do commit & push: $ JEKYLL_ENV=production bundle exec jekyll build
cd into _site: $ cd _site
target all files for commit: $ git add -A
commit them: git commit -am 'Yeah. Built from subdir'
and push your site to GitHub-Pages: git push