Add Jekyll redirections to existing posts

gistfile1.rb

#!/usr/bin/ruby

# Loop through the posts and add the redirections YML front-matter
# used by the plugin described here:
#
#   http://www.marran.com/tech/creating-redirects-with-jekyll/
#
# This is a total hack job, just enough to get the job done. I'm
# sure there's a better way to do this. 

Dir.foreach('./_posts') do |item|
  next if item == '.' || item == '..'

  # Strip the extension off
  filename = item.split('.').first

  # Break down the filename
  parts = filename.split('-')

  # Recombine it into the folders and permalink
  permalink = "#{parts.shift}/#{parts.shift}/#{parts.shift}/#{parts.join('-')}"

  puts permalink

  file_contents = File.read "./_posts/#{item}"
  
  # Add redirection YML
  new_contents = file_contents.gsub(
    /\s---/,
    %Q{

redirection:
- #{permalink}/

---}
  )

  File.open("./_posts/#{item}", 'w') do |file|
    file.puts new_contents
  end
end