nix: add pre-commit-hooks

flake.nix

@@ -16,15 +16,38 @@
       repo = "nixpkgs";
       ref = "nixos-unstable";
     };
+
+    pre-commit-hooks = {
+      type = "github";
+      owner = "cachix";
+      repo = "pre-commit-hooks.nix";
+      ref = "master";
+      inputs = {
+        flake-utils.follows = "futils";
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
   };
 
-  outputs = { self, futils, nixpkgs } @ inputs:
-    futils.lib.eachSystem futils.lib.allSystems (system:
+  outputs = { self, futils, nixpkgs, pre-commit-hooks } @ inputs:
+    futils.lib.eachDefaultSystem (system:
       let
         inherit (nixpkgs) lib;
         pkgs = nixpkgs.legacyPackages.${system};
       in
       {
+        checks = {
+          pre-commit = pre-commit-hooks.lib.${system}.run {
+            src = ./.;
+
+            hooks = {
+              nixpkgs-fmt = {
+                enable = true;
+              };
+            };
+          };
+        };
+
         devShell = pkgs.mkShell {
           name = "blog";
 
@@ -32,6 +55,8 @@
             gnumake
             hugo
           ];
+
+          inherit (self.checks.${system}.pre-commit) shellHook;
         };
       }
     );