Change the theme of an existing Jekyll installation

  Pull New Theme
git checkout --orphan newtheme
git rm -rf .
git clean -dfx

git remote add upstream https://github.com/johnotander/pixyll.git
git fetch upstream
git pull upstream master

bundler install
jekyll serve

  Merge Changes
git checkout master -- _posts
git show master:_config.yml > _config.yml.old
git checkout upstream/master -- about.md

  Replace the master branch
git checkout newtheme
git merge -s ours master
git checkout master
git merge newtheme

git push
git branch -d newtheme

  Updating the theme
git pull upstream master