docker config to deploy jekyll blog using github actions

action.yml

 # Ok, here the keys are pretty much self explanatory :)
    name: 'Deploy new version'
    description: 'Setup Ruby env and build new site version'
    author: 'Sujay Kundu'
    runs:
      using: 'docker'
      image: 'Dockerfile'

Dockerfile

   # Our Docker image will be based on ruby:2-slim
    # it is a very light docker image.
    FROM ruby:2-slim
    LABEL author="Sujay Kundu"
    LABEL version="1.0.0"

    # Lets install all dependencies
    # including git and Bundler 2.1.4
    ENV BUNDLER_VERSION 2.1.4
    RUN apt-get update && \
        apt-get install --no-install-recommends -y \
        bats \
        build-essential \
        ca-certificates \
        curl \
        libffi6 \
        make \
        shellcheck \
        libffi6 \
        git-all \
        && gem install bundler:2.1.4 \
        && bundle config --global silence_root_warning 1

    # This is our entrypoint to our custom scripts
    # more about that in a sec
    COPY entrypoint.sh /

    # Use the entrypoint.sh file as the container entrypoint
    # when Github executes our Docker container
    ENTRYPOINT ["sh", "/entrypoint.sh"]

entrypoint.sh

  #!/bin/bash
    # Exit immediately if a pipeline returns a non-zero status.
    set -e

    echo "🚀 Starting deployment action"

    # Here we are using the variables
    # - GITHUB_ACTOR: It is already made available for us by Github. It is the username of whom triggered the action
    # - GITHUB_TOKEN: That one was intentionally injected by us in our workflow file.
    # Creating the repository URL in this way will allow us to `git push` without providing a password
    # All thanks to the GITHUB_TOKEN that will grant us access to the repository
    REMOTE_REPO="https://${GITHUB_ACTOR}:${GITHUB_TOKEN}@github.com/${GITHUB_REPOSITORY}.git"

    # We need to clone the repo here.
    # Remember, our Docker container is practically pristine at this point
    git clone $REMOTE_REPO repo
    cd repo

    # Install all of our dependencies inside the container
    # based on the git repository Gemfile
    echo "⚡️ Installing project dependencies..."
    bundle install

    # Build the website using Jekyll
    echo "🏋️ Building website..."
    JEKYLL_ENV=production bundle exec jekyll build
    echo "Jekyll build done"

    # Now lets go to the generated folder by Jekyll
    # and perform everything else from there
    cd _site

    echo "☁️ Publishing website"

    # We don't need the README.md file on this branch
    rm -f README.md

    # Now we init a new git repository inside _site
    # So we can perform a commit
    git init
    git config user.name "${GITHUB_ACTOR}"
    git config user.email "${GITHUB_ACTOR}@users.noreply.github.com"
    git add .
    # That will create a nice commit message with something like:
    # Github Actions - Fri Sep 6 12:32:22 UTC 2019
    git commit -m "Github Actions - $(date)"
    echo "Build branch ready to go. Pushing to Github..."
    # Force push this update to our gh-pages
    git push --force $REMOTE_REPO master:gh-pages
    # Now everything is ready.
    # Lets just be a good citizen and clean-up after ourselves
    rm -fr .git
    cd ..
    rm -rf repo
    echo "🎉 New version deployed 🎊"