Ignore negation works differently than it Git

[alerque]

I just struggled with a Flake for a while and finally figured out some sources were being excluded from the Flake because ignore rules were being handled differently than Git itself does.

!scripts/*.in
scripts/*

In Git, this will result in all the autoconf template files ending with .in being tracked and everything else in the scripts directory (the AC_CONFIG_FILE output in my case) ignored. With gitignoreSource the order of operations is different and everything is getting ignored.

[roberth]

It seems that only the opposite order is tested:

gitignore.nix/tests/testdata.nix

Lines 84 to 89 in 637db32

	2-*/[^.]*
	!2-*/1?
	!2-*/30
	!/2-*/70
	!/40
	!50