Github flavored markdown to HTML

convert.rb

require 'rubygems'
require 'bundler/setup'

require 'github/markup'
require 'html/pipeline'

file = ARGV[0]
abort("#{file} does not exist.") unless File.exists?(file)

html = GitHub::Markup.render(file)
pipeline = HTML::Pipeline.new [
  HTML::Pipeline::MarkdownFilter,
  HTML::Pipeline::SyntaxHighlightFilter
]

puts pipeline.call(html)[:output].to_s

Gemfile

source 'https://rubygems.org'

gem 'github-markup'
gem 'github-markdown'
gem 'github-linguist'
gem 'html-pipeline'