One other quick timeline

April 5, 2005:
BitMover decides to "focus exclusively" on its commercial version
No more free-beer BitKeeper for the kernel

April 7, 2005:
Linus posts the first version of git
"really nasty (but also very fast)"

April 20, 2005:
2.6.12-rc3 released
Done entirely with git

August, 2005 (maybe):
Git 1.0 released