macros are undocumented at buildout.org

I was looking for documentation on the "<=" section macro format.

I didn't see anything at http://www.buildout.org and this search finds nothing:
  http://www.google.com/search?q=site:www.buildout.org+macros

I think it's reasonable that people will look for this documentation there. It would be good if the docs from http://pypi.python.org/pypi/zc.buildout could be included on the site.