make git-hooks opt-in

pre-commit hook break git commits and are disruptive.
Therefore people that want to enable this feature, should enable it locally instead.
I.e. treefmt will also check untracked files that are not meant for the current commit.

devShell.nix

@@ -1,4 +1,4 @@
-{ inputs, ... }:
+{ ... }:
 {
   perSystem =
     {
@@ -9,7 +9,6 @@
     }:
     let
       writers = pkgs.callPackage ./pkgs/builders/script-writers.nix { };
-      inherit (pkgs.callPackage inputs.git-hooks { }) lib;
 
       ansiEscapes = {
         reset = ''\033[0m'';
@@ -22,11 +21,6 @@
       select-shell = writers.writePython3Bin "select-shell" {
         flakeIgnore = [ "E501" ];
       } ./pkgs/scripts/select-shell.py;
-
-      # run treefmt before each commit
-      install-pre-commit-hook =
-        with lib.git-hooks;
-        pre-commit (wrap.abort-on-change config.treefmt.build.wrapper);
     in
     {
       devShells.default = pkgs.mkShell {
@@ -41,8 +35,6 @@
           config.treefmt.build.wrapper
         ];
         shellHook = ''
-          ${install-pre-commit-hook}
-
           echo -e "${ansiEscapes.green}switch to another dev-shell using: select-shell${ansiEscapes.reset}"
         '';
       };

flake.lock

@@ -40,22 +40,6 @@
         "type": "github"
       }
     },
-    "git-hooks": {
-      "flake": false,
-      "locked": {
-        "lastModified": 1716413087,
-        "narHash": "sha256-nSTIB7JeJGBGsvtqlyfhUByh/isyK1nfOq2YMxUOFJQ=",
-        "owner": "fricklerhandwerk",
-        "repo": "git-hooks",
-        "rev": "99a78fcf7dc03ba7b1d5c00af109c1e28ced3490",
-        "type": "github"
-      },
-      "original": {
-        "owner": "fricklerhandwerk",
-        "repo": "git-hooks",
-        "type": "github"
-      }
-    },
     "nixlib": {
       "locked": {
         "lastModified": 1712450863,
@@ -149,7 +133,6 @@
       "inputs": {
         "disko": "disko",
         "flake-parts": "flake-parts",
-        "git-hooks": "git-hooks",
         "nixos-generators": "nixos-generators",
         "nixos-images": "nixos-images",
         "nixpkgs": "nixpkgs",

flake.nix

@@ -21,8 +21,6 @@
     flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
     treefmt-nix.url = "github:numtide/treefmt-nix";
     treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
-    git-hooks.url = "github:fricklerhandwerk/git-hooks";
-    git-hooks.flake = false;
   };
 
   outputs =

scripts/pre-commit

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# To install:
+# ln -sf ../../scripts/pre-commit .git/hooks/pre-commit
+set -o errexit
+set -o nounset
+set -o pipefail
+
+readarray staged < <(git diff --name-only --cached)
+[[ ${#staged[@]} = 0 ]] && exit
+unstash() {
+  local ret=$?
+  set +e
+  git stash pop -q
+  exit "$ret"
+}
+git stash push --quiet --keep-index --message "pre-commit"
+trap unstash EXIT
+nix fmt
+{
+  changed=$(git diff --name-only --exit-code);
+  status=$?;
+} || true
+if [[ $status -ne 0 ]]; then
+  exec 1>&2
+  echo Files changed by pre-commit hook:
+  echo "$changed"
+  exit $status
+fi