Added nix check and pre commit hook for formatting (nix-community#220)

* Added nix check and pre commit hook for formatting

* Removed nix fmt check from CI

.envrc

@@ -0,0 +1,7 @@
+use_flake() {
+  watch_file flake.nix
+  watch_file flake.lock
+  eval "$(nix print-dev-env --profile "$(direnv_layout_dir)/flake-profile")"
+}
+
+use flake

.github/workflows/check.yml

@@ -12,4 +12,3 @@ jobs:
         with:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
       - run: nix flake check
-      - run: nix fmt -- -c .

.gitignore

@@ -1,2 +1,3 @@
 .tmp
 result
+.pre-commit-config.yaml

flake.nix

@@ -7,10 +7,14 @@
   inputs.beautysh.url = "github:lovesegfault/beautysh";
   inputs.beautysh.inputs.nixpkgs.follows = "nixpkgs";
 
+  inputs.pre-commit-hooks.url = "github:cachix/pre-commit-hooks.nix";
+  inputs.pre-commit-hooks.inputs.nixpkgs.follows = "nixpkgs";
+
   outputs = {
     self,
     nixpkgs,
     flake-utils,
+    pre-commit-hooks,
     ...
   } @ inputs:
     with nixpkgs.lib;
@@ -62,9 +66,23 @@
             };
           extractRustAnalyzerPkg = pkgs.callPackage extractRustAnalyzer {};
         in {
-          checks = import ./tests/checks.nix {
-            inherit pkgs;
-            makeNixvim = self.legacyPackages."${system}".makeNixvim;
+          checks =
+            (import ./tests/checks.nix {
+              inherit pkgs;
+              makeNixvim = self.legacyPackages."${system}".makeNixvim;
+            })
+            // {
+              pre-commit-check = pre-commit-hooks.lib.${system}.run {
+                src = ./.;
+                hooks = {
+                  alejandra.enable = true;
+                };
+              };
+            };
+          devShells = {
+            default = pkgs.mkShell {
+              inherit (self.checks.${system}.pre-commit-check) shellHook;
+            };
           };
           packages = {
             docs = pkgs.callPackage (import ./docs.nix) {