I prefer Mercurial. It's easier to teach to non-programmers and it has a less confusing cli. Git has a terrible mess of cli options. I have also used Fossil and that is very nicely designed. Played a bit with bzr and darcs in the past. For many users Mercurial or Fossil would be the better tool for them than Git. Also checkout EasyMercurial, it's a suburb GUI for Mercurial.
Oh, I think I've seen this. If I remember correctly SQLite uses it.
Thanks.
every one talking about jujutsu. learning git from jujutsu more easy than using git directly. it is more convenient. I just want using it for my project in future.
Not exactly what you asked, but I use TortoiseGit and Git Cola 99% of the time and the CLI only for weird stuff (after making a back up branch).