When I do something that is not trivial and needs some research, I try to summarize it and write it down, in case that I will need later to do the same thing again. It may also be useful for other people that could be trying to do something similar.
Recently I made this visualization for contributors to https://l10n.org.al for the last two years (2012-2013). This visualization was done with gource. It was a bit of hacking, so I would like to describe here how I did it.