Each subdirectory is a standalone project which you can build using Alire and flash to a Raspberry Pi Pico. It is also possible to run the debugger - see the project's own README for details. You can copy whichever project is most similar to your use case to a new location and initialize your git repo there.
This is a relatively new project and you may encounter bugs. Please file GitHub issues or join the development discussion on Gitter: https://gitter.im/ada-lang/raspberrypi-pico.