My take: Messages like this...

> Updated Gemfile.lock and added new dependencies (coderay, concurrent-… …ruby, crass, date, pry, method_source, public_suffix, puma, nio4r) and updated existing dependencies (rack-test, regexp_parser, xpath, nokogiri, racc, pg). Also added new files for a user authentication feature.

Describe the "what" but not the "why". Even "user auth wip" would be helpful. It's like having autogenerated code comments like:

// initialize variable i for later use in a loop

int i = 3;

GPT can struggle to see the forest from the trees. For example, if generating a dozen or so files with `rails g scaffold post` a GPT-generated commit message may simply list all the individual items "Created new post views, new post controller, new post model.. etc" when "Generated a posts scaffold" would have been more general and useful message.

GPT sometimes 'sees' the bigger picture though, for example when I commit a new rails app, instead of listing the individual files, it instead generated: "Added all files for a new Rails application, including controllers, models, views, tests, and configuration files." It could have said "new rails app", but it wasn't too ineloquent.

Spot on. The coffee already says what. If it doesn’t, probably could use a refactor.

Code doesn’t say why, who and especially why not. (It sometimes may say when, but the important when is always yesterday anyway.)