[Low Priority] Improve speed measurement

[Anachron]

I get ridiculous speed statements when I sync from time to time.

Today I got

sudo xbps-install -Su
[*] Updating repository `https://repo-default.voidlinux.org/current/x86_64-repodata' ...
x86_64-repodata: 308KB [avg rate: -14GB/s]
[*] Updating repository `https://repo-default.voidlinux.org/current/nonfree/x86_64-repodata' ...
x86_64-repodata: 13KB [avg rate: 211MB/s]

Edit: Both results are wrong, btw.

[fvalasiad]

Well short syncs also give me crazy speed sometimes, just got 12GB/s after syncing. Didn't manage a negative value though.

I imagine though that having lengthier interactions will actually give more accurate results, so I struggle finding reason why anyone would care.

Might look at it for fun.

[Duncaen]

Yes there is no way to actually make this reliable for small downloads. Negative is a simple bug where incomplete downloads that are begin continued will be counted wrong iirc.