feat: add a few ways to easily run/author small rust packages

lib/templates/rust/nix/packages.nix

@@ -18,8 +18,9 @@ let
       ];
     */
 
-    cargoHash = pkgs.lib.fakeHash;
-    useFetchCargoVendor = true;
+    cargoLock = {
+      lockFile = ./Cargo.lock;
+    };
   };
 in
 {

packages/default.nix

@@ -9,4 +9,8 @@ in
   # installer = pkgs.callPackage ./installer.nix { };
   ghostty-terminfo = pkgs.callPackage ./ghostty-terminfo.nix { };
   forgejo-actions-container = pkgs.callPackage ./forgejo-actions-container.nix { };
+  hello_world = pkgs.callPackage ./rust/hello_world { };
+  hello_world_script = pkgs.writeScriptBin "hello_world_script" (
+    builtins.readFile ./rust/hello_world_script/main.rs
+  );
 }

packages/rust/hello_world/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "hello_world"
+version = "0.1.0"

packages/rust/hello_world/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "hello_world"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

packages/rust/hello_world/default.nix

@@ -0,0 +1,16 @@
+{
+  rustPlatform,
+}:
+let
+  inherit (builtins) fromTOML readFile;
+  pname = "hello_world";
+  src = ./.;
+  package = rustPlatform.buildRustPackage {
+    inherit pname src;
+    version = (fromTOML (readFile "${src}/Cargo.toml")).package.version;
+    cargoLock = {
+      lockFile = ./Cargo.lock;
+    };
+  };
+in
+package

packages/rust/hello_world/src/main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello, world!");
+}

packages/rust/hello_world_script/main.rs

@@ -0,0 +1,15 @@
+#!/usr/bin/env nix
+//! ```cargo
+//! [dependencies]
+//! time = "0.1.25"
+//! ```
+/*
+#!nix shell nixpkgs#rustc nixpkgs#rust-script nixpkgs#cargo --command rust-script
+*/
+fn main() {
+    for argument in std::env::args().skip(1) {
+        println!("{}", argument);
+    }
+    println!("{}", std::env::var("HOME").expect(""));
+    println!("{}", time::now().rfc822z());
+}