It's not. The diff, which is the sole input to GPT-3 here, does not carry the causal context - that is,
why the change was made. Nor does it carry the broader understanding necessary to summarize the
what succinctly and accurately - things like high-level design terms that mostly exist on diagrams or in issue trackers, but not in the code itself. By adding those details in a commit message, the author can add extra information.
And yes, technically they could do it in comments, which would allow GPT-3 to process it. Except, I think it's highly unlikely for a coder using ChatGPT to write commit messages for them to actually author useful comments on their own. If they write any at all, they'll probably use ChatGPT (or Copilot) for that too.
