feat: cleanup configs

justfile

@@ -26,6 +26,23 @@ clean:
     sudo nix-store --optimise
     sudo {{ if os() == "macos" { "darwin-rebuild switch" } else { "nixos-rebuild boot" } }} --flake .#{{host}}
 
+# Format every .nix file in the repo with nixfmt (RFC 166 style).
+# Runs inside the devShell, so it works with or without direnv loaded.
+fmt:
+    nix develop -c bash -c "find . -name '*.nix' -not -path './iso/*' -not -path './.direnv/*' -exec nixfmt {} +"
+
+# Lint Nix for anti-patterns (statix) and dead/unused bindings (deadnix).
+# Exits nonzero on findings, so it doubles as a CI check.
+lint:
+    nix develop -c statix check .
+    nix develop -c deadnix --fail .
+
+# Preview what the next `rebuild` would change: build the target system
+# without switching, then diff it against the running one.
+diff:
+    nix build --out-link /tmp/notfiles-next {{ if os() == "macos" { ".#darwinConfigurations." + host + ".system" } else { ".#nixosConfigurations." + host + ".config.system.build.toplevel" } }}
+    nix develop -c nvd diff /run/current-system /tmp/notfiles-next
+
 # Generate Ed25519 SSH keys for each named service (default: github gradescope).
 # Override:  just gen-keys gitlab bitbucket
 gen-keys *services='github gradescope h2p durrantlab signing_git scienting_git scienting_static_sites':