In fact, it is really easy to set up:
- In Google Analytics, click on "Add Website Profile".
- Verify that "Add a Profile for a new domain" is selected.
- Enter the Google Code URL of your project. For example "code.google.com/p/eclipse-printers/".
- Click "Finish >"
- In Google Code, click on the "Administer" tab of your project.
- At the bottom of the "Project Summary" page, paste the tracking number into the field "Analytics profile number".
- Click on "Save Changes".
- In Google Analytics, click on "Done".
- After 24 hours the first data will show up in Google Analytics.
PS: I'm not sure whether this is new functionality or whether this option has been there from the start. I only started using Google Analytics long after I started using Google Code so I might not have been paying attention that field back then.