Add nix-fmt pre-commit hook

.gitignore

@@ -1,2 +1,5 @@
+# Pre-commit config
+.pre-commit-config.yaml
+
 # Virtual Machines Disks
 *.qcow2

flake.nix

@@ -13,9 +13,14 @@
       url = "github:nix-community/home-manager/release-23.05";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    pre-commit-hooks = {
+      url = "github:cachix/pre-commit-hooks.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { nixpkgs, nixpkgs-unstable, ... } @ inputs:
+  outputs = { nixpkgs, nixpkgs-unstable, pre-commit-hooks, ... } @ inputs:
     let
       system = "x86_64-linux";
 
@@ -32,9 +37,23 @@
         ];
       });
     in
-    {
+    rec {
       formatter.${system} = pkgs.nixpkgs-fmt;
 
+      checks.${system}.pre-commit-check = pre-commit-hooks.lib.${system}.run {
+        src = ./.;
+        hooks = {
+          nixpkgs-fmt = {
+            enable = true;
+            name = pkgs.lib.mkForce "Nix files format";
+          };
+        };
+      };
+
+      devShells.${system}.default = pkgs.mkShell {
+        inherit (checks.${system}.pre-commit-check) shellHook;
+      };
+
       nixosConfigurations = {
         Bacon = nixpkgs.lib.nixosSystem
           (import ./bacon.nix { inherit inputs system pkgs; });

system/default.nix

@@ -172,10 +172,10 @@
         description = "oui oui baguette";
         languages = [ "eng" ];
         symbolsFile =
-        let
-          ouioui = (pkgs.callPackage ./qwerty-fr.nix { });
-        in
-        "${ouioui}/usr/share/X11/xkb/symbols/us_qwerty-fr";
+          let
+            ouioui = (pkgs.callPackage ./qwerty-fr.nix { });
+          in
+          "${ouioui}/usr/share/X11/xkb/symbols/us_qwerty-fr";
       };
 
       libinput = {