NB: I was wrong about extensions not using helpcategories. I checked something different than I thought I had. They do add categories to their commands.
May 7 2019
[registering the gpg command category] doesn't actually seem to work for making it appear in hg help.
May 5 2019
May 4 2019
May 3 2019
May 2 2019
I think this is a fine idea -- it is more robust, because it does not depend on getting the commit syntax right, but on knowing the right place. It also means commit messages (for developers, one per commit) don't have to do double duty as release notes (for users, one per functional change).
Apr 29 2019
Changing this script affects hg.1 and hg.1.html. I have uploaded the original output, and the output after this patch stack; links below.