I don't particularly want a commit log at the top of every function, TBH. If I'm looking for the history and context of a change, I want to look at the commit log. If I want a description of the current version, I look in the docs (and yeah, sometime I can only piece together why something is the way it is now by looking through how it's changed. But documenting each change has a much better chance of addressing questions like "why did it work and now it doesn't" then trying to get the docs perfect will.)