You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: command_line.rb
    path of file: ./repos/chef/lib/chef/chef_fs
    
    the code of the file until where you have to start completion: #
# Author:: John Keiser (<jkeiser@chef.io>)
# Copyright:: Copyright (c) Chef Software Inc.
# License:: Apache License, Version 2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may
    
        def diff_text(old_path, new_path, old_value, new_value)
          # Copy to tempfiles before diffing
          # TODO don't copy things that are already in files!  Or find an in-memory diff algorithm

          new_tempfile = Tempfile.new("new")
          new_tempfile.write(new_value)
          new_tempfile.close

          old_tempfile = Tempfile.new("old")
          old_tempfile.write(old_value)
          old_tempfile.close

          result = Chef::Util::Diff.new.udiff(old_tempfile.path, new_tempfile.path)
          result = result.gsub(/^--- #{old_tempfile.path}/, "--- #{old_path}")
          result = result.gsub(/^\+\+\+ #{new_tempfile.path}/, "+++ #{new_path}")
          result
        rescue => e
          "!!! Unable to diff #{old_path} and #{new_path} due to #{e}"
        ensure
          old_tempfile.close!
          new_tempfile.close!
        end
      end