DISCLAIMER This project is still very much Work in Progress...
Testing OpenRewrite recipes for upgrading Grails projects
The grails6 folder contains a Grails 6 project and OpenRewrite recipes for upgrading to the upcoming Grails 7
The grails3 folder contains a Grails 3 project and OpenRewrite recipes for upgrading to Grails 6
Grails 2 is old and uses Gant for dependency management and building, writing an OpenRewrite recipe for upgrading is probably not that easy...
Take a look at Sørens GitHub projects and his initialGrails2Converter project
If you want please try out the recipes on your projects and report any issues I would be happy to improve the project to make upgrading Grails easier for all of us.