title: Tool like 2to3, except for merges
body: <p>I maintain a fork of my project for Python 3.1. When I initially made the port from 2.6, I used 2to3, but now I constantly have to merge new code from the 2.6 fork into the 3.1 fork. How can I perform the 2to3 operation on these merges automatically? (I use git, if it matters.)</p>