What is git?
It's a significant enough event in computing to merit its own wikipedia entry: http://en.wikipedia.org/wiki/Git
Here's some criticism of the idea (it sounds like this was repeated many times by different people):
http://lists.gnu.org/archive/html/gnu-arch-users/2005-04/msg00237.html
Drop me a line if you find interesting rebuttals of this argument (I've read Linus's own)