Picocli is a modern framework for building powerful, user-friendly, GraalVM-enabled command line apps with ease. It supports colors, autocompletion, subcommands, and more. In 1 source file so apps can include as source & avoid adding a dependency. Written in Java, usable from Groovy, Kotlin, Scala, etc.
Mixins can use model transformers to make changes to the model. This is useful to allow for mix-in reuse while changing option names and void clashes.