nix: allow fallback for shell.nix in case user can't use flakes

Author: aster-void

.envrc

@@ -1 +1,2 @@
-use flake
+watch_file shell.nix
+use flake || use nix

flake.nix

@@ -16,30 +16,7 @@
         pkgs = nixpkgs.legacyPackages.${system};
       in {
         formatter = pkgs.alejandra;
-        devShells.default = pkgs.mkShell {
-          packages = with pkgs; [
-            # general
-            lefthook # precommit
-            gitleaks # secret leak detection
-            just # task runner
-            litecli # sqlite CLI client with advanced features
-
-            # JS
-            bun # runner / tester
-            # biome # style checker / linter ... replaced by deno because biome doesn't support HTML and svelte
-            deno # used to format svelte
-
-            # Nix
-            alejandra # formatter
-            nil # langserver
-            statix # nix linter
-            deadnix # code analyzer (detects dead code)
-          ];
-
-          shellHook = ''
-            lefthook install
-          '';
-        };
+        devShells.default = pkgs.callPackage ./shell.nix {};
       }
     );
 }

shell.nix

@@ -0,0 +1,26 @@
+{pkgs ? import <nixpkgs> {}}:
+pkgs.mkShell {
+  name = "How Match development";
+  packages = with pkgs; [
+    # general
+    lefthook # precommit
+    gitleaks # secret leak detection
+    just # task runner
+    litecli # sqlite CLI client with advanced features
+
+    # JS
+    bun # runner / tester
+    # biome # style checker / linter ... replaced by deno because biome doesn't support HTML and svelte
+    deno # used to format svelte
+
+    # Nix
+    alejandra # formatter
+    nil # langserver
+    statix # nix linter
+    deadnix # code analyzer (detects dead code)
+  ];
+
+  shellHook = ''
+    lefthook install
+  '';
+}