I think it refers to two things: the title of the book about how Linus create Linux "Just for Fun. The Story of an Accidental Revolutionary", and the fact that Git had to be created to continue effective work on Linux kernel (after BitKeeper fiasco).
From the start of the article:
Linus Torvalds once wrote in a book that he created Linux just for fun, but it ended up sparking a revolution. Git, his second major creation, also an accidental revolution.
The partial checkout support in Git is getting improved. Take a look, maybe it now solves your problems.
Support for large repositories via
scalar
works also for Linux (though not everything is ported; as main body of work on supporting large repositories was created to deal with the size of MS Windows repository, it started with Windows-only support / optimization first).There are alternatives to submodules, like https://github.com/chronoxor/gil