Linux kernel development was managed with tarballs and patches for the first 10 years, until BitKeeper was selected in 2002, then of course Git in 2005.

Source: http://en.wikipedia.org/wiki/Linux_kernel#Revision_control Also see Linus Torvalds' Google Tech Talk on Git starting around 2:45 http://www.youtube.com/watch?v=4XpnKHJAok8