linguist: Implement more robust gitattributes handling
We've seen Gitaly crash in production 1. The crash originally happened on 2.
This was caused by a bug in go-git. To make the code more robust we re-implement the checking of gitattributes(5) using the git-check-attr(1) command.
Closes: #4523 (closed)
Closes: #4522 (closed)
Edited by Toon Claes