mercurial

So, Mercurial, or "hg" in short. One of the two revision control systems originally written for being the Linux kernel's BitKeeper replacement - in the end, git was chosen for that job, but Mercurial lived on nevertheless. The requirement of being suitable for kernel development implied two features: performance (although git is still a tiny bit faster) and distributed development methodologies. Both are also present in git, and in fact, the two systems are very similar in scope, paradigms and usage patterns.

While git is written in pure C, Mercurial mostly consists of Python code, with only small, critical code paths implemented in C. This has benefits for Mercurial's portability, as can even be observed with other SoC students. git is pretty much focused on just Linux, whereas Mercurial can also be installed more easily on Windows and other Unixes. Not that straightforward graphical tools are yet as mature as the ones that exist for CVS or SVN.