Introduce nixf-tidy

[kachick]

nix-community/nixd#497
https://discourse.nixos.org/t/list-of-nix-linters/19279/9
NixOS/nixpkgs#330066
NixOS/nixpkgs#332695
https://github.com/inclyc/flakes/blob/168b2fb0c66c9946037afaf1b4bb884e3b58b465/.github/workflows/nixf-tidy.yml#L25C13-L25C36

[kachick]

💭 Without this, zed and the default nixd integration displays many warnings

[kachick]

Draft

git ls-files '*.nix' | xargs -I{} bash <<'BASH'
echo -n '{}: '
git diff --exit-code --quiet <(printf '[]\n') <(<{} nixf-tidy --pretty-print --variable-lookup)
echo "$?"
BASH


git ls-files '*.nix' | xargs -I{} bash <(<<'BASH'
echo -n "$1: "
BASH
) {}


git ls-files '*.nix' | xargs -I{} bash -c '
echo -n "{}: "
git diff --exit-code --quiet <(printf "[]\n") <(<{} nixf-tidy --pretty-print --variable-lookup)
echo "$?"
'

[kachick]

When refactoring in #943, it throws much parse-redundant-paren

https://github.com/nix-community/nixd/blob/0f3c0c730e5cb9414f3b269dc9b36062a0e5236e/libnixf/src/Basic/diagnostic.py#L49-L51

I'm not positive for these, because of I wish nixfmt-rfc-style should cover these if need.

And nixf-tidy does not take CLI options to modify behavior. And the returned JSON does not include severity. Might be dropped 🤔