If you use Google Code to host open source projects; now when you fix / update a code, you can easily close the loop by putting an issue tracker command in your commit-log message. There’re commit-log commands to: Easily set an issue's status to Fixed; Update any aspect of the issue, and add a comment; Enter a new issue; Request a code review

The most common case is to close the issue as Fixed. For example, your commit-log message might be:

Now, your commit links to the issues, the issues are closed, and a back-link is added from each issue to the revision.

More info: Wiki