Improve exclude matching

[d-Rickyy-b]

Currently the matching doesn't perfectly work like .gitignore filtering.

[d-Rickyy-b]

Should work more like that: https://labs.consol.de/de/development/git/2017/02/22/gitignore.html

Also nice tool for testing globbing: https://globster.xyz/

[d-Rickyy-b]

Improved in 0b25309 - still not perfect.

The best performing way of excluding would be to skip processing of certain sub directories during filepath.Walk: https://golang.org/pkg/path/filepath/#WalkFunc

We just need to return filepath.Skipdir within the filepath.Walk WalkFn