Feature Request: --exclude parameter and builtin default excludes

[phip1611]

Hi there!

Currently, nixfmt . fails in projects where I use direnv as it tries to reformat something in .direnv:

nixfmt: ./.direnv/flake-inputs/pgildni8kbdhq7b28006b7px1qjf6jyp-source/nix: openTempFileWithDefaultPermissions: permission denied (Read-only file system)

A nice solution would be:

• automatic excludes (gitignore file? hardcoded list, such as .direnv)
• -E/--exclude parameter

Would be cool to see this in the future. Keep up the great work!

[infinisil]

This is a known issue, but we decided to defer file filtering to other tools: #151 (comment)

[phip1611]

Thanks!