We've all thought "what is this thing supposed to do?" or "why was this done that way" moment when looking through codebases and unless there's documentation or you can find the author, the answer is often hard to find. There are many options to document code from comments to internal wikis, so I'll discuss a heuristic for evaluating the options based on the accessibility (how far away is the answer?) and accuracy (how likely is it that what I'm reading is out of date?) to build a case that the git commit message is likely where you should spend your energy documenting.