Are all patches created equal?

that's actually a very very clever idea. It would reward both people who do code clean ups by removal of duplicate code snippets as well people who inject non copy-pasted code snippets, including usable documentation and comemnts.

Like everything else its subject to being gamed. Obviously random bits of obfuscated code in a commit would show up with high entropy and thus high value. However such a piece of code would probably be selected against in human review/sign off as it would be highly unreadable. So I think the entropy metric strikes a good balance there.

I think as this idea is probably make a great comparison metric with just the raw commits as a positive impact assessment that is understandable to the main audience without getting too bogged down into very detailed scoring algorithms. From an information theory pov, commits which caused the overall codebase to go up in entropy is a higher positive impact than those which lower entropy. We can actually start asking the question who is just pumping out trivial commits that are overall low impact, and find a way to encourage them to take the leap to something high impact.

The side effect of that of course is that, over time, if people strive to reach the top of the entropy impact metric, we could see the kernel codebase become less and less compressible. Hopefully this is offset by large amounts of cleanup that shrinks the overall size of the codebase to offset the entropy increase leading to less compression.

-jef