This Tcl script is what I used in order to generate the graph you can find at http://antirez.com/news/98. It’s really quick & dirty, more a trow away program than anything else, but probably could be reused or modified in the future in order to visualize other similar data or an updated version of the same data.
The usage is trivial:
./genhtml.tcl > output.html
The generated HTML is quite broken but good enough to grab a screenshot from the browser. Feel free to improve it if you got time / interest.
Note that the code filtering the tags, and the hardcoded branch name, does not make the script, as it is, able to analyze a different repository. However the changes needed are trivial.