I wrote a hackish Greasemonkey script to do something similar last year that just did it on the fly. Also tried to get a simple measure of how much was spam just by searching for simple keywords in the edit records.

I'd like to revisit the idea some time, because I'm sure you can also capture more details about the nature of editing (ie, how often are different parts edited, what keywords get added and removed most frequently, how many people are involved or is it just a revert war between two stubborn editors...) within a useful visualisation.