Adding "read more" to Jekyll

postmore.rb

module Jekyll
  module PostMore
    def postmorefilter(input, url, text)
      m = /(?<morestring><!--\s*more\s*-->)/.match(input)
      if m
        input.split(m[:morestring]).first + "<p class=\"more\"><a href=\"#{url}\">#{text}</a></p>"
      else
        input
      end
    end
  end
end

Liquid::Template.register_filter(Jekyll::PostMore)