Any changes are correctly updated in the buffer immediately if flydiff is enabled. So I think it works at this point.

But I notice that if I commit those changes, instead of using built-in vc or magit, but via git cli from terminal, which is how I get used to doing all reversion stuffs, the buffer won't be updated and those indicators in fringe are still there.

I inspected using vc and the buffer then is updated on the fly. So is this behavior a desired result that only revision operations performed inside Emacs will trigger diff-hl-update to update buffer on time?