You can mark your project as moved on your admin page. If you change your mind, you can clear the setting by clicking the publish button.
Setting the "Project Moved" Flag
Once a project has been successfully exported to GitHub, you will want to update your project's homepage on Google Code to avoid confusion.
Some project owners simply update their project homepage's text to indicate it has moved to GitHub. For example subtext or bwapi.
Another option is to set the Google Code "project moved" flag. When set, attempts to access the project will take users to an interstitial page indicating the new project location. In the future, the page will automatically redirect to well-known project hosting services such as github.com.
To set the "project moved" flag, navigate to your project's advanced admin page, at https://code.google.com/p//adminAdvanced.
Once there, enter the new project home page URL under "project moved". For example: https://github.com/google/kythe. Finally click the "Project Moved" button.
If you need to "un-move" a project, you can go back to the /adminAdvanced page at a later time and click "Publish". This will restore your project to its original state, before the move.