flake.nix: remove treefmt-nix input (#6782)

Removing input until I have time to migrate usage to a dev flake for all
the dev dependencies.

.github/workflows/test.yml

@@ -23,7 +23,7 @@ jobs:
           exit 1
         fi
     - run: nix-build --show-trace -A docs.jsonModuleMaintainers
-    - run: nix flake check
+    - run: ./format --ci
     - run: nix-shell --show-trace . -A install
     - run: yes | home-manager -I home-manager=. uninstall
     - run: nix-shell -j auto --show-trace --arg enableBig false --pure tests -A run.all

flake.lock

@@ -18,28 +18,7 @@
     },
     "root": {
       "inputs": {
-        "nixpkgs": "nixpkgs",
-        "treefmt-nix": "treefmt-nix"
-      }
-    },
-    "treefmt-nix": {
-      "inputs": {
-        "nixpkgs": [
-          "nixpkgs"
-        ]
-      },
-      "locked": {
-        "lastModified": 1743748085,
-        "narHash": "sha256-uhjnlaVTWo5iD3LXics1rp9gaKgDRQj6660+gbUU3cE=",
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "rev": "815e4121d6a5d504c0f96e5be2dd7f871e4fd99d",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "treefmt-nix",
-        "type": "github"
+        "nixpkgs": "nixpkgs"
       }
     }
   },

flake.nix

@@ -1,20 +1,12 @@
 {
   description = "Home Manager for Nix";
 
-  inputs = {
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-
-    treefmt-nix = {
-      url = "github:numtide/treefmt-nix";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
-  };
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
 
   outputs =
     {
       self,
       nixpkgs,
-      treefmt-nix,
       ...
     }:
     {
@@ -54,23 +46,9 @@
     // (
       let
         forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed;
-
-        treefmtEval = forAllSystems (
-          system:
-          treefmt-nix.lib.evalModule nixpkgs.legacyPackages.${system} {
-            # Formatting configuration
-            programs = {
-              nixfmt.enable = true;
-            };
-          }
-        );
       in
       {
-        checks = forAllSystems (system: {
-          formatting = treefmtEval.${system}.config.build.check self;
-        });
-
-        formatter = forAllSystems (system: treefmtEval.${system}.config.build.wrapper);
+        formatter = forAllSystems (system: nixpkgs.legacyPackages.${system}.nixfmt-tree);
 
         packages = forAllSystems (
           system:

format

@@ -14,7 +14,7 @@ for arg do
             echo "$0 [-c]"
             exit
             ;;
-        -c)
+        --ci)
             nixfmt_args+=("$arg")
             ;;
         -*)