Parse .gitattributes

[AUnicornWithNoLife]

Summary 💡

.gitattributes overides what language a file extension is mapped to

example (from a unity project):

*.compute linguist-language=HLSL
*.shader linguist-language=HLSL

Motivation 🔦

onefetch should be accurate to the repository's structure, and should report data in the same way github does

[spenserblack]

I do agree that we need some form of overrides. Especially as long as we use tokei. But, unless we use data sourced directly from linguist, I don't think we should use the linguist overrides.

BTW, gengo (#1152) can take overrides from .gitattributes 😉