create Atom feed for middleman

feed.builder

---
layout: false
---
require 'open3'

xml.instruct!
xml.feed "xmlns" => "http://www.w3.org/2005/Atom" do
  xml.title "Sample Site"
  xml.link "href" => "http://example.com"
  xml.updated Time.now
  # gitのコミットの日付で更新日付を設定するようにし、ソートする
  resources = sitemap.resources.sort_by do |resource|
    # see. https://git-scm.com/docs/git-log#Documentation/git-log.txt-emcIem
    o, e, s = Open3.capture3("git log --pretty=format:%cI -n1 #{resource.source_file}")
    resource.add_metadata({updated: o})
    o
  end.reverse
  resources.each do |resource|
    xml.entry do
      xml.title resource.metadata[:page][:title]
      xml.link "href" => "http://example.com#{resource.url}"
      xml.updated resource.metadata[:updated]
    end if resource.destination_path =~ /\.html$/
  end
end