A nice concept, but it doesn't really have much to do with Git. It's just another SCM system, and the concepts are just as applicable to e.g. Mercurial as Git. There are enough differences from Git to make it quite incompatible (named repository, incremented commit IDs, single parents et c.).
The point is to implement gradually. For example, in the concepts covered in part 1, multiple parents was not required, hence it was left. It should make sense to the reader why something was implemented and why it does what it does.
Its concepts might apply to other VCS. But that is immaterial, Git is what we are trying to understand here.
