Add commit hook and flake check for formatting

.envrc

@@ -0,0 +1 @@
+use flake

.pre-commit-config.yaml

@@ -0,0 +1 @@
+/nix/store/aimf4r2pn4gapwcm87hbwx73r40cj89i-pre-commit-config.json

formatter.nix

@@ -1,14 +1,27 @@
 {
+  self,
   nixpkgs,
   treefmt-nix,
   flake-utils,
+  pre-commit-hooks,
   ...
 }:
 flake-utils.lib.eachDefaultSystem (
   system: let
     pkgs = nixpkgs.legacyPackages.${system};
     treefmtEval = treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
+    treefmtWrapper = treefmtEval.config.build.wrapper;
   in {
-    formatter = treefmtEval.config.build.wrapper;
+    packages.formatter = treefmtWrapper;
+    formatter = self.packages.${system}.formatter;
+    checks.pre-commit-check = pre-commit-hooks.lib.${system}.run {
+      src = ./.;
+      hooks = {
+        treefmt = {
+          enable = true;
+          package = treefmtWrapper;
+        };
+      };
+    };
   }
 )

shell.nix

@@ -1,4 +1,5 @@
 {
+  self,
   flake-utils,
   nixpkgs,
   ...
@@ -7,6 +8,7 @@ flake-utils.lib.eachDefaultSystem (system: let
   pkgs = nixpkgs.legacyPackages.${system};
 in {
   devShells.default = pkgs.mkShell {
-    buildInputs = with pkgs; [ansible];
+    inherit (self.checks.${system}.pre-commit-check) shellHook;
+    buildInputs = self.checks.${system}.pre-commit-check.enabledPackages ++ [pkgs.ansible];
   };
 })