I have created a rsyslog "family tree" showcasing how the various branches and versions go together. It is a condensed graph of the git DAG and shows a few feature branches as an example. I personally think it provides a good overview of how rsyslog work progresses (click picture for larger version).
In red is the git master branch, blue are currently supported stable branches. Branch head "v1-stable" is dotted, because it is no longer officially supported. Dashed nodes are versions on feature branches, solid nodes are versions on main branches. Solid lines are direct ancestors, dashed lines indicate that there are some versions in between. Lots of feature branches have not been show. Bug fixes are typically applied to the oldest code experiencing the problem and then merged into the more recent versions, thus the code flow for bug fixes is kind of reverse. This bug fixing code flow is not shown inside the graph.
Note that you can use gitk to create the full DAG from the git archive. The purpose of my effort is to show the relationships that are well-hidden in gitk's detailled view.
I have written a much more elaborate post about the "evolution of software", unfortunately, it is available currently only in German (with very questionable results by Google Translate).