For shits and giggles, I had a go at writing a script that could rewrite all the commits in a branch with LLM generated commits. Couldn't work out how to do the commit changing, tried cherry picking, but it doesnt work well for conflicts (had no idea that was possible). But, I can report timings at least.

On my M1 16GB macbook air, each commit was summarised in about 10s. So its a plausible approach if you just do all your commits, and then run a script to fix up the messages, go get a glass of water and you'll come back to automatic messages.

If it's of interest to you, I can share the script, its a starting point, but I am pretty ashamed of it :D