Shameless plug:
We built xltrail[0] (cloud and self-hosted SaaS) that lets you see the diffs for sheets, VBA, and a couple other things. You put in your git repo and it just works. You can also have a manual versioning option where you upload new versions of the same file and you get the same result.
We also have the open source git extension Git XL[1] that lets you see VBA diffs locally.