duf reports human units incorrectly on macOS

[notrobpike]

When using -h|-H, I recognize that on linux (ubuntu 20 anyway) df reports base-2 units as 'G', T' etc, and reports base-10 units exactly the same. So, the output alone is not enough to tell you what you're looking at, and we generally assume base-2.

But on macOS, -h uses a correct binary prefix Gi, Ti, etc. I think on Linux it's arguable which is the correct choice, but on macOS, duf should be following the lead of the OS supplied df.

I'll note that while the output is "correct" (distinguishable) on macOS, the manual for df(1) is wrong. They mention base-2 but then use the words for base-10 in the description.