class GitHubPages::Dependencies

corresponding version to which it shall be locked in the runtime dependencies.
and versions locked. Any plugin for Pages must be specified here with a
Dependencies is where all the public dependencies for GitHub Pages are defined,

def self.gems

https://help.github.com/articles/using-jekyll-with-pages
For more information see:
Jekyll and related dependency versions as used by GitHub Pages. 
def self.gems
  VERSIONS.merge(GitHubPages::Plugins::THEMES)
end

def self.version_report 

def self.version_report
  require "html/pipeline/version"
  require "sass/version"
  require "safe_yaml/version"
  require "nokogiri"
  {
    "ruby" => RUBY_VERSION,
    # Gem versions we're curious about
    "github-pages" => VERSION.to_s,
    "html-pipeline" => HTML::Pipeline::VERSION,
    "sass" => Sass.version[:number],
    "safe_yaml" => SafeYAML::VERSION,
    "nokogiri" => Nokogiri::VERSION,
  }
end

def self.versions

Useful for programmatically querying for the current-running version
Versions used by GitHub Pages, including github-pages gem and ruby version 
def self.versions
  gems.merge version_report
end