Comparing two GitHub Issues List

Is there a way to compare two GitHub Issues lists?

What I need is a programatic way to compare the items that exist in two GitHub repositories (repo A and repo B),  do a diff, and list the ones that don't exist in repo B (i.e. which ones were not copied from repo A to repo B)

Recently we moved the TeamMentor issues/bug list into the public repository: https://github.com/TeamMentor/Master/issues

Before (when started to use GitHub for TeamMentor development) we used the private repository https://github.com/DinisCruz/TeamMentor-v3.0/issues

When we did the switch, we manually moved a number of issues into the new public repository, but I want to make sure we don't lose anything (since these issue's list are also our brain-dump of ideas for future releases)

So, any tools or services that currently do this?