build(flake): add template

.templates/flake/.envrc

@@ -0,0 +1,5 @@
+if has nix; then
+    use flake .
+fi
+
+# vim: ft=sh

.templates/flake/.gitignore

@@ -0,0 +1,3 @@
+# Nix generated
+/.pre-commit-config.yaml
+result

.templates/flake/README.md

@@ -0,0 +1,3 @@
+# `sandbox`
+
+A description fitting in one single line.

.templates/flake/flake.nix

@@ -0,0 +1,27 @@
+{
+  description = "Sandbox template";
+
+  outputs = {
+    self,
+    nixpkgs,
+  }: let
+    supportedSystems = [
+      "x86_64-linux"
+    ];
+    forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
+    nixpkgsFor = forAllSystems (system: import nixpkgs {inherit system;});
+  in {
+    devShells = forAllSystems (system: let
+      pkgs = nixpkgsFor.${system};
+    in {
+      default = pkgs.mkShell {
+        name = "sandbox-nix-shell";
+        buildInputs = with pkgs; [
+          just
+        ];
+      };
+    });
+  };
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs";
+}

.templates/shell/.envrc

@@ -0,0 +1,5 @@
+if has nix; then
+    use nix
+fi
+
+# vim: ft=sh

.templates/shell/shell.nix

@@ -0,0 +1,14 @@
+{
+  pkgs ? (
+    let
+      inherit (builtins) fetchTree fromJSON readFile;
+      inherit ((fromJSON (readFile ../flake.lock)).nodes) nixpkgs;
+    in
+      import (fetchTree nixpkgs.locked) {}
+  ),
+}:
+pkgs.mkShell {
+  packages = with pkgs; [
+    hello
+  ];
+}

Justfile

@@ -2,3 +2,15 @@
 build-readme:
 	@python make_readme.py
 	@sh .github/make-readme.sh
+
+# Create sandbox
+create-sandbox sandbox:
+	@mkdir -v "{{justfile_directory()}}/{{sandbox}}"
+	@cd "{{justfile_directory()}}/{{sandbox}}" \
+		&& nix flake init -t "{{justfile_directory()}}#templates.shell"
+
+# Create sandbox with Flake
+create-sandbox-flake sandbox:
+	@mkdir -v "{{justfile_directory()}}/{{sandbox}}"
+	@cd "{{justfile_directory()}}/{{sandbox}}" \
+		&& nix flake init -t "{{justfile_directory()}}#templates.flake"

flake.nix

@@ -19,14 +19,26 @@
   }: let
     supportedSystems = ["x86_64-linux"];
   in
-    flake-utils.lib.eachSystem supportedSystems (system: let
+    {
+      templates = {
+        flake = {
+          path = ./.templates/flake;
+          description = "Sandbox with flake";
+        };
+        shell = {
+          path = ./.templates/shell;
+          description = "Sandbox with only a Nix shell";
+        };
+      };
+    }
+    // flake-utils.lib.eachSystem supportedSystems (system: let
       pkgs = import nixpkgs {inherit system;};
-    in rec {
+    in {
       checks = {
         pre-commit-check = pre-commit-hooks.lib.${system}.run {
           src = ./.;
 
-          hooks = with pkgs; {
+          hooks = {
             make_readme = {
               enable = true;
               name = "make-readme";