Nix flake: add cargo-nightly for udeps

flake.nix

@@ -15,9 +15,16 @@
           pkgs = import nixpkgs {
             inherit system overlays;
           };
-          nu_plugin_bash_env = pkgs.writeShellScriptBin "nu_plugin_bash_env"
-            (builtins.replaceStrings [ "jq" "(cat)" " sed " ] [ "${pkgs.jq}/bin/jq" "(${pkgs.coreutils}/bin/cat)" " ${pkgs.gnused}/bin/sed " ]
-              (builtins.readFile ./nu_plugin_bash_env));
+          # cargo-nightly based on https://github.com/oxalica/rust-overlay/issues/82
+          nightly = pkgs.rust-bin.selectLatestNightlyWith (t: t.default);
+          cargo-nightly = pkgs.writeShellScriptBin "cargo-nightly" ''
+            export RUSTC="${nightly}/bin/rustc";
+            exec "${nightly}/bin/cargo" "$@"
+          '';
+          # TODO:
+          # nu_plugin_bash_env = pkgs.writeShellScriptBin "nu_plugin_bash_env"
+          #   (builtins.replaceStrings [ "jq" "(cat)" " sed " ] [ "${pkgs.jq}/bin/jq" "(${pkgs.coreutils}/bin/cat)" " ${pkgs.gnused}/bin/sed " ]
+          #     (builtins.readFile ./nu_plugin_bash_env));
         in
         with pkgs;
         {
@@ -26,11 +33,13 @@
               bashInteractive
               jq
               cargo-modules
+              cargo-nightly
               cargo-udeps
               rust-bin.stable.latest.default
             ];
           };
-          packages.default = nu_plugin_bash_env;
+          # TODO: build package from Rust crate
+          # packages.default = nu_plugin_bash_env;
         }
       );
 }