Add treefmt

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

flake.nix

@@ -32,12 +32,20 @@
     };
 
     disko = {
-      url = "github:nix-community/disko";
+      type = "github";
+      owner = "nix-community";
+      repo = "disko";
+      ref = "master";
+
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
     sops-nix = {
-      url = "github:Mic92/sops-nix";
+      type = "github";
+      owner = "Mic92";
+      repo = "sops-nix";
+      ref = "master";
+
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
@@ -49,22 +57,47 @@
     };
 
     nur = {
-      url = "github:nix-community/NUR";
+      type = "github";
+      owner = "nix-community";
+      repo = "NUR";
+      ref = "master";
+
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
     flake-utils = {
-      url = "github:numtide/flake-utils";
+      type = "github";
+      owner = "numtide";
+      repo = "flake-utils";
+      ref = "main";
+
       inputs.systems.follows = "systems";
     };
 
+    treefmt-nix = {
+      type = "github";
+      owner = "numtide";
+      repo = "treefmt-nix";
+      ref = "main";
+
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
     astal = {
-      url = "github:aylur/astal";
+      type = "github";
+      owner = "aylur";
+      repo = "astal";
+      ref = "main";
+
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
     ags = {
-      url = "github:aylur/ags";
+      type = "github";
+      owner = "aylur";
+      repo = "ags";
+      ref = "main";
+
       inputs = {
         nixpkgs.follows = "nixpkgs";
         astal.follows = "astal";
@@ -115,10 +148,11 @@
         };
       };
     }
-    // inputs.flake-utils.lib.eachDefaultSystem (
+    // inputs.flake-utils.lib.eachSystem [ "x86_64-linux" ] (
       system:
       let
         pkgs = nixpkgs.legacyPackages.${system};
+        treefmt = inputs.treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
       in
       {
         devShells = {
@@ -131,7 +165,8 @@
           python = import ./hosts/common/shells/python { inherit pkgs; };
         };
 
-        formatter = pkgs.nixfmt-rfc-style;
+        formatter = treefmt.config.build.wrapper;
+        checks.formatting = treefmt.config.build.check self;
       }
     );