Vincent Massol has published an article explaining how the XWiki project has switched from using CLIRR to using Revapi for automatically ensuring API backward compatibility.
This is key for the XWiki project since XWiki is a development platform: it provides APIs for easily developing collaborative web applications. As such it needs to ensure that those APIs keep working over time and that an application or extension developed several years ago will continue to work fine when installed on the latest version of XWiki.
For more on XWiki's best practice regarding backward compatibility, check the project's development practices.
