doctor.rb

def check_for_outdated_homebrew
  HOMEBREW_REPOSITORY.cd do
    timestamp = if File.directory? ".git"
      `git log -1 --format="%ct" HEAD`.to_i
    else
      (HOMEBREW_REPOSITORY/"Library").mtime.to_i
    end

    if Time.now.to_i - timestamp > 60 * 60 * 24 then <<-EOS.undent
      Your Homebrew is outdated
      You haven't updated for at least 24 hours, this is a long time in brewland!
      EOS
    end
  end
end