Implement treefmt's stdin spec
Full disclosure: the treefmt stdin spec is not yet finalized (see https://github.com/numtide/treefmt/pull/586). However, nothing prevents us from implementing the version of it that I hope will be approved.
This completes https://github.com/NixOS/nixfmt/issues/305.
I have very little haskell knowledge. I'm sure there are issues with this implementation. Be kind, I'm excited to learn more!
This pull request has been mentioned on NixOS Discourse. There might be relevant details there:
https://discourse.nixos.org/t/formatting-team-meeting-2025-11-11/72019/4
This pull request has been mentioned on NixOS Discourse. There might be relevant details there:
https://discourse.nixos.org/t/formatting-team-meeting-2025-11-25/72427/1