Exclude auto-generated files from hlint hints

[andreasabel]

I am seeing this always for my Parser.hs generated from Parser.y by happy:

I think it does not make sense to include the generated files into hlint hinting, as generators may opt for robustness rather than beauty. In this particular instance, happy issues {-# LANGUAGE PartialTypeSignatures #-} twice, but I could not care less, and I cannot fix it without patching happy.

Suggestion: exclude auto-generated files from hlint, at least by default.

I am on HLS 2.11.0.0 (latest released).