A simple way to manage a Jekyll static site that uses plugins

heavies_publish.rb

require 'jekyll'
module Heavies
  GITHUB_REPOSITORY="heavies/beta"
  SOURCE_BRANCH="source"
  PUBLISHED_BRANCH="gh-pages"
  PUBLISHED_DIR=".published"
  ROOT_DIR=File.expand_path(File.join(File.dirname(__FILE__), '..', '..'))

  module Publish
    def self.dir
      File.join(ROOT_DIR, PUBLISHED_DIR)
    end

    def self.source_branch
      SOURCE_BRANCH
    end

    def create_published_dir
      system "git clone -b #{PUBLISHED_BRANCH} git@github.com:#{GITHUB_REPOSITORY}.git #{Publish.dir}"
    end

    def clean_published_dir
      Dir.chdir(Publish.dir) do
        system "git add -A"
        system "git reset --hard"
        system "git checkout #{PUBLISHED_BRANCH}"
        system "git pull --ff-only -ff origin #{PUBLISHED_BRANCH}"
      end
    end

    def remove_published_dir
      FileUtils.rm_rf(Publish.dir)
    end

    def generate_site
      # Uses the standard configuration settings in _config.yml
      # Overides the destination
      Jekyll::Site.new(Jekyll.configuration({
        "destination" => Publish.dir
      })).process
    end

    def ready?
      regex = /\A## #{Publish.source_branch}\Z/m
      !regex.match(read_current_status).nil?
    end

    def publish_site
      sha1 = publishing_sha1
      Dir.chdir(Publish.dir) do
        system "git add -A"
        message =  "Site updated at #{Time.now.utc}\n\n"
        message += "Updated to: #{sha1}\n"
        message += "CHANGES: #{compare_url(sha1)}"
        system "git commit -m #{message.shellescape}"
        system "git push origin #{PUBLISHED_BRANCH}"
      end
    end

    def compare_url(sha1=publishing_sha1)
      compare_url = "https://github.com/#{GITHUB_REPOSITORY}/compare/#{comparison(sha1)}"
    end

    def comparison(sha1=publishing_sha1)
      "#{last_sha1}...#{sha1}"
    end

    private
    def read_current_status
      Dir.chdir(ROOT_DIR) do
        system 'git fetch'
        return `git status --porcelain -b`.strip
      end
    end

    def publishing_sha1
      Dir.chdir(ROOT_DIR) do
        return `git rev-parse HEAD`.strip
      end
    end

    def last_sha1
      Dir.chdir(Publish.dir) do
        body = `git log --pretty=format:%b -1`
        return body[/^Updated to: (.+)$/,1]
      end
    end
  end
end

Rakefile

require 'heavies_publish'
require 'launchy'

desc 'Publish the site'
task :publish => 'publish:publish'

namespace :publish do
  include Heavies::Publish

  directory Heavies::Publish.dir
  file Heavies::Publish.dir do
    create_published_dir
  end

  desc 'Get the latest published version'
  task :clean => Heavies::Publish.dir do
    clean_published_dir
  end

  desc 'Remove the published directory'
  task :clobber do
    remove_published_dir
  end

  task :generate => :clean do
    generate_site
  end

  desc 'Compare to the currently published site'
  task :compare => :clean do
    system "git log #{comparison}"
  end

  namespace :compare do
    require 'launchy'
    desc 'View github compare view between source HEAD and last published version'
    task :github do
      Launchy.open(compare_url)
    end
  end

  task :ready do
    unless ready?
      puts "You may only publish the '#{Heavies::Publish.source_branch}' branch, and it must be fully up-to-date and pushed."
      exit(1)
    end
  end

  task :publish => [:ready, :generate] do
    publish_site
  end
end