I have had some good ideas and some stupid ideas for semantic history, and many very mixed prototypes. The simplest option, and what I'll probably go with, is just a table of commits-modifying-this-thing. But that's not all the information; for example, a linear list of commits doesn't convey branch/merge topology well. I'm not sure how useful that information is, but I'd kinda like to see it.
The data I collect is two things: first, we can do a semantic git-diff operation in the backend; and second, we search-index the diffs so you can say "which commits modify entity X" and get a fast answer. That's what the UI will do when you focus on a function.
I use off-the-shelf TS grammars and write custom queries for them. I've got a custom abstraction in the backend that lets you query for ranges of nodes at once, which is how we jump to the top of comments above a function rather than to the function definition itself.
Your back-burner project is exactly where Asqi is headed -- and in fact, the backend for this is 100% done in Asqi but the frontend doesn't show the data yet. The idea is to determine things like, "two branches modify function X in two different ways" and even if the diffs don't collide, you get to see that there's a potential semantic conflict coming up. There's some potential opportunity to use past change data to detect when a function is sensitive to multiple editors, or when it's just a big list of calls/hooks or some such where it doesn't matter so much. So in the long term, I think of it as "how important is this potentially interesting conflict scenario" as some type of user-attention number that is priority-sorted so the user sees most-important first.
(Btw, I would personally not like to hear that my pet project was being implemented by a non-free product; the silver lining here is that Asqi will always let you analyze private repos locally if you don't need to pull them automatically -- i.e. if you have local clones -- so it's probably free for what you're doing unless you're launching a SaaS product. I may also add some type of data export API later so you can use the Asqi backend to power other frontends.)
