title: Diff between two entire directories that contain source and output the result in a textfile
body: <p>I have two directories that contain directories and source files. One directory contains the modified source code and the other one is unmodified source code. And I want to see what source code was modified and see the modified part of the code. And I also want to output the result to a single text file.</p>
  
  <p>I know I have to use the diff tool but I'm not sure what options should I use. Do I need to create a script for this, or is there a one line command to do the task?</p>