annabunches.net/_plugins/markdown_and_sign.rb

# Adds metadata to the post object for linking to the source page.
Jekyll::Hooks.register :posts, :pre_render do |post, payload|
  if post.path =~ /\.md$/
    post.data['md_file'] = "/#{post.data['category']}/#{post.basename}"
  end
end

# Copy all of the source markdown files directly into the destination.
Jekyll::Hooks.register :site, :post_write do |site|
  dest = site.dest
  site.posts.docs.select{|p| p.path =~ /\.md$/}.each do |post|
    FileUtils.cp(post.path, "#{dest}/#{post.data['category']}/#{post.basename}")
  end
end