You can clone with
HTTPS or Subversion.
It'd be useful to support something like the segmented lines of Protovis. I'm pretty sure you can do segmented areas using the existing d3.svg.area and d3.split, but segmented lines require computing miter joints.
I have implemented miter joints in these examples:
It would be nice to package up the joint calculation in reusable form. Perhaps something in d3.geom would work.