I now use the Drush module Git Release Notes which does the same as below. I mention it in the article below but at the time it did not support Drupal 7.
Looking for easy way to make release notes for your Drupal project. Below is a simple linux script(should work for OS X) for outputing all the git commit messages between 2 tags. It will also make links to the related commits on drupalcode.org for your project.