flake.nix: add nixfmt pre-commit hook

.gitignore

@@ -6,3 +6,4 @@ config.tf.json
 .terraform.lock.hcl
 secrets/*
 !secrets/*.age
+.pre-commit-config.yaml

flake.lock

@@ -278,6 +278,22 @@
         "type": "github"
       }
     },
+    "flake-compat_5": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1696426674,
+        "narHash": "sha256-kvjfFW7WAETZlt09AgDn1MrtKzP7t90Vf7vypd3OL1U=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "0f9255e01c2351cc7d116c072cb317785dd33b33",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
     "flake-parts": {
       "inputs": {
         "nixpkgs-lib": [
@@ -385,6 +401,27 @@
         "type": "github"
       }
     },
+    "gitignore": {
+      "inputs": {
+        "nixpkgs": [
+          "pre-commit-hooks",
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1709087332,
+        "narHash": "sha256-HG2cCnktfHsKV0s4XW83gU3F57gaTljL9KNSuG6bnQs=",
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "rev": "637db329424fd7e46cf4185293b9cc8c88c95394",
+        "type": "github"
+      },
+      "original": {
+        "owner": "hercules-ci",
+        "repo": "gitignore.nix",
+        "type": "github"
+      }
+    },
     "grapevine": {
       "inputs": {
         "attic": "attic",
@@ -631,6 +668,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-stable_2": {
+      "locked": {
+        "lastModified": 1720386169,
+        "narHash": "sha256-NGKVY4PjzwAa4upkGtAMz1npHGoRzWotlSnVlqI40mo=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "194846768975b7ad2c4988bdb82572c00222c0d7",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-24.05",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "nixpkgs_2": {
       "locked": {
         "lastModified": 1723151389,
@@ -678,6 +731,29 @@
         "type": "github"
       }
     },
+    "pre-commit-hooks_2": {
+      "inputs": {
+        "flake-compat": "flake-compat_5",
+        "gitignore": "gitignore",
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "nixpkgs-stable": "nixpkgs-stable_2"
+      },
+      "locked": {
+        "lastModified": 1723202784,
+        "narHash": "sha256-qbhjc/NEGaDbyy0ucycubq4N3//gDFFH3DOmp1D3u1Q=",
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "rev": "c7012d0c18567c889b948781bc74a501e92275d1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "cachix",
+        "repo": "pre-commit-hooks.nix",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "agenix": "agenix",
@@ -691,6 +767,7 @@
         ],
         "nix-gerrit": "nix-gerrit",
         "nixpkgs": "nixpkgs_2",
+        "pre-commit-hooks": "pre-commit-hooks_2",
         "terranix": "terranix"
       }
     },

flake.nix

@@ -29,6 +29,9 @@
       repo = "grapevine-fork";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
+    pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";
   };
 
   outputs =
@@ -37,6 +40,7 @@
       nixpkgs,
       terranix,
       colmena,
+      pre-commit-hooks,
       ...
     }@inputs:
     let
@@ -113,6 +117,21 @@
 
               (pkgs.callPackage ./lib/colmena-wrapper.nix { })
             ];
+
+            inherit (inputs.self.checks.${system}.pre-commit) shellHook;
+          };
+        }
+      );
+
+      checks = forEachSystem' (
+        { system, pkgs, ... }:
+        {
+          pre-commit = pre-commit-hooks.lib.${system}.run {
+            src = ./.;
+            hooks.nixfmt = {
+              enable = true;
+              package = pkgs.nixfmt-rfc-style;
+            };
           };
         }
       );