"Projects outside the kernel began adopting Git shortly after its release. A key landmark in Git adoption came when Keith Packard, one of the lead developers of the X Window System, published two influential articles in 2007."
It's exactly what it sounds like.
Looks like a successor to Blosxom and PyBlosxom and maybe also IkiWiki.
I agree with all of this except the suggestion that Torvalds is responsible for it. He popularized this model of development, but he didn't invent it.