modules/homebrew: add homebrew.cargoPackages option

Add support for `cargo "pkg"` entries in the generated Brewfile. Homebrew
Bundle supports installing Rust crates via `cargo install`; the `rust`
formula is automatically installed if not already present.

modules/homebrew.nix

@@ -562,16 +562,18 @@ in
   options.homebrew = {
     enable = mkEnableOption ''
       {command}`nix-darwin` to manage installing/updating/upgrading Homebrew taps, formulae,
-      casks, Mac App Store apps, Go packages, and Docker containers, using Homebrew Bundle.
+      casks, Mac App Store apps, Go packages, Cargo crates, and Docker containers, using Homebrew
+      Bundle.
 
       Note that enabling this option does not install Homebrew, see the Homebrew
       [website](https://brew.sh) for installation instructions.
 
       Use the [](#opt-homebrew.brews), [](#opt-homebrew.casks),
       [](#opt-homebrew.masApps), [](#opt-homebrew.goPackages),
-      [](#opt-homebrew.whalebrews), and [](#opt-homebrew.vscode) options to list the
-      Homebrew formulae, casks, Mac App Store apps, Go packages, Docker containers,
-      and Visual Studio Code extensions you'd like to install. Use the
+      [](#opt-homebrew.cargoPackages), [](#opt-homebrew.whalebrews), and
+      [](#opt-homebrew.vscode) options to list the Homebrew formulae, casks, Mac App
+      Store apps, Go packages, Cargo crates, Docker containers, and Visual Studio Code
+      extensions you'd like to install. Use the
       [](#opt-homebrew.taps) option, to make additional formula repositories available to
       Homebrew. This module uses those options (along with the
       [](#opt-homebrew.caskArgs) options) to generate a Brewfile that
@@ -789,6 +791,18 @@ in
       '';
     };
 
+    cargoPackages = mkOption {
+      type = with types; listOf str;
+      default = [ ];
+      example = [ "ripgrep" ];
+      description = ''
+        List of Rust packages to install using {command}`cargo install`.
+
+        Homebrew will automatically install the {command}`rust` formula if it is not already
+        installed.
+      '';
+    };
+
     whalebrews = mkOption {
       type = with types; listOf str;
       default = [ ];
@@ -867,6 +881,7 @@ in
       + mkBrewfileSectionString "Mac App Store apps"
         (mapAttrsToList (n: id: ''mas "${n}", id: ${toString id}'') cfg.masApps)
       + mkBrewfileSectionString "Go packages" (map (v: ''go "${v}"'') cfg.goPackages)
+      + mkBrewfileSectionString "Cargo packages" (map (v: ''cargo "${v}"'') cfg.cargoPackages)
       + mkBrewfileSectionString "Docker containers" (map (v: ''whalebrew "${v}"'') cfg.whalebrews)
       + mkBrewfileSectionString "Visual Studio Code extensions" (map (v: ''vscode "${v}"'') cfg.vscode)
       + optionalString (cfg.extraConfig != "") ("# Extra config\n" + cfg.extraConfig);