rust: change default rust flake

flakes/rust/flake.nix

@@ -1,31 +1,58 @@
 {
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-    utils.url = "github:numtide/flake-utils";
+    flake-utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, nixpkgs, utils }:
-    utils.lib.eachDefaultSystem (system:
+  outputs = { self, nixpkgs, flake-utils }:
+    let
+      inherit (builtins) fromTOML readFile substring;
+
+      cargoToml = fromTOML (readFile ./Cargo.toml);
+      version = "${cargoToml.package.version}+${substring 0 8 self.lastModifiedDate}_${self.shortRev or "dirty"}";
+
+      # FIXME: rename mkHello
+      mkHello = { lib, rustPlatform, ... }:
+        rustPlatform.buildRustPackage {
+          pname = cargoToml.package.name;
+          inherit version;
+
+          src = lib.cleanSource ./.;
+          cargoLock.lockFile = ./Cargo.lock;
+
+          doCheck = true;
+        };
+    in
+    {
+      # FIXME: rename hello overlay with package name
+      overlays.hello = final: prev: {
+        hello = prev.callPackage mkHello;
+      };
+      overlays.default = self.overlays.hello;
+    }
+    //
+    flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs { inherit system; };
-        cargoToml = with builtins; (fromTOML (readFile ./Cargo.toml));
+        # FIXME: rename hello
+        hello = pkgs.callPackage mkHello { };
       in
-      rec {
-        packages.default = pkgs.rustPlatform.buildRustPackage {
-          inherit (cargoToml.package) name version;
-          src = nixpkgs.lib.cleanSource ./.;
-          doCheck = true;
-          cargoLock.lockFile = ./Cargo.lock;
+      {
+        packages = {
+          inherit hello;
+          default = hello;
         };
 
-        apps.default = utils.lib.mkApp {
-          inherit (cargoToml.package) name;
-          drv = packages.default;
+        # FIXME: rename hello app with program path
+        apps.hello = {
+          type = "app";
+          program = "${hello}/bin/hello";
         };
+        apps.default = self.apps.${system}.hello;
 
-        devShell = with pkgs; mkShell {
-          packages = [ cargo rustc rustfmt clippy rust-analyzer ];
-          RUST_SRC_PATH = rustPlatform.rustLibSrc;
+        devShell = pkgs.mkShell {
+          packages = with pkgs; [ cargo rustc rustfmt clippy rust-analyzer ];
+          RUST_SRC_PATH = pkgs.rustPlatform.rustLibSrc;
         };
       });
 }