Comment 1 for bug 198728

I think bazzar used diff to do this. For example, if you have two files a1.txt and a2.txt as below.

a1.txt
=====
bar = Attribute("The bar.")
frob = Attribute("The frob name.")

name = Attribute("The frob name as text.")
=====

a2.txt
=====
baz = Attribute("The qux baz.")
bar = Attribute("The qux bar.")
frob = Attribute("The frob name.")

name = Attribute("The frob name as text.")
=====

Now check following commands

diff -u b.txt a.txt
==================================
--- b.txt 2008-11-17 16:08:14.000000000 -0600
+++ a.txt 2008-11-17 16:09:05.000000000 -0600
@@ -1,4 +1,5 @@
-bar = Attribute("The bar.")
+baz = Attribute("The qux baz.")
+bar = Attribute("The qux bar.")
 frob = Attribute("The frob name.")

 name = Attribute("The frob name as text.")
==================================

So, we need to find a package for diff utility and may be change this bug for that package if you feel like.