An example is the "About branch begin-concurrent-pnu-wal2" at the top of the page https://www.sqlite.org/src/timeline?r=begin-concurrent-pnu-w... - the page shows all check-ins for the branch, and the Wiki at the top gives a summary of what that branch is about.
Another example is the detailed discussion in the "About" section for check-in https://www.sqlite.org/src/info/718ead555b09892f - important information that records the thinking about this commit but which seems too prolix for a check-in comment.
Let me know your thoughts on this idea.
In the last week I have been quite charmed by many of Fossil ideas, I will for sure try this feature too.
Personally, how I tend to work is if there’s some link between commit and ticketing system I can refer to, it’s about the best you can expect.