cleanup nix

Co-authored-by: uku <hi@uku.moe>

flake.nix

@@ -1,33 +1,34 @@
 {
-  description = "Description for the project";
+  description = "C++ UML diagram generator based on Clang";
 
   inputs = {
-    flake-parts.url = "github:hercules-ci/flake-parts";
-    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    nixpkgs.url = "nixpkgs";
+
+    flake-parts = {
+      url = "github:hercules-ci/flake-parts";
+      inputs.nixpkgs-lib.follows = "nixpkgs";
+    };
   };
 
-  outputs = inputs@{ flake-parts, ... }:
-    flake-parts.lib.mkFlake { inherit inputs; } {
-      imports = [];
-      systems = [ "x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin" ];
-      perSystem = { config, self', inputs', pkgs, system, ... }: {
+  outputs = {flake-parts, ...} @ inputs:
+    flake-parts.lib.mkFlake {inherit inputs;} {
+      systems = ["x86_64-linux" "aarch64-linux" "aarch64-darwin" "x86_64-darwin"];
 
-        packages.default = config.packages.clang-uml;
-        packages.clang-uml = pkgs.callPackage packaging/nix/default.nix { };
+      perSystem = {
+        self',
+        pkgs,
+        ...
+      }: {
+        packages = {
+          default = self'.packages.clang-uml;
+          clang-uml = pkgs.callPackage ./packaging/nix {};
+        };
 
         devShells.default = pkgs.mkShell {
-          packages = with pkgs; [
-            # C++ Compiler is already part of stdenv
-            cmake
-            llvmPackages_latest.libllvm
-            yaml-cpp
-            ccache
-            elfutils
-            pkg-config
-            clang
-            libclang
-          ];
+          inputsFrom = [self'.packages.clang-uml];
         };
+
+        formatter = pkgs.alejandra;
       };
     };
 }