Zero.

> There also isn’t a clear way to see a “diff” of the visual changes being made on Github which makes the feedback a bit more difficult — we have to download the file and manually compare with the previous version.

This also ignores the fact that design assets are massive regardless, more than what git is intended to be used for in the first place.

Since we use Sketch files for our design there isn't yet a clear way to see a diff comparison. We tried using other services but there still isn't an ideal solution for that yet.