Ruby-cvs CVS history interface

I’d like to make a change/dependency graph of our code base similar
to the example at the GraphViz site, e.g.,

or Figure 4 in,

I’d really like to use ruby-cvs, but it is lacking an interface
to CVS’s history command (it’s on ruby-cvs’ TODO list). Has anyone
happened to have hacked one in already or should I just backtick
or ‘system’ it… ?