Prefer stable pkgs for bash and basics

NixOS/nixpkgs#300055
kachick/dotfiles#532

flake.nix

@@ -5,32 +5,35 @@
     #   - https://discourse.nixos.org/t/differences-between-nix-channels/13998
     # How to update the revision
     #   - `nix flake update --commit-lock-file` # https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-flake-update.html
-    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
+    edge-nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     flake-utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, nixpkgs, flake-utils }:
+  outputs = { self, nixpkgs, edge-nixpkgs, flake-utils }:
     flake-utils.lib.eachDefaultSystem (system:
-      let pkgs = nixpkgs.legacyPackages.${system};
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        edge-pkgs = edge-nixpkgs.legacyPackages.${system};
       in {
         # Q. Why nixfmt? Not nixpkgs-fmt and alejandra?
         # A. nixfmt will be official
         # - https://github.com/NixOS/nixfmt/issues/153
         # - https://github.com/NixOS/nixfmt/issues/129
         # - https://github.com/NixOS/rfcs/pull/166
-        formatter = pkgs.nixfmt;
+        formatter = edge-pkgs.nixfmt;
         devShells.default = with pkgs;
           mkShell {
             buildInputs = [
               # https://github.com/NixOS/nix/issues/730#issuecomment-162323824
               # https://github.com/kachick/dotfiles/pull/228
               bashInteractive
+              edge-pkgs.nixfmt
+              edge-pkgs.nil
 
-              nixfmt
-              nil
-              dprint
-              typos
-              go-task
+              edge-pkgs.dprint
+              edge-pkgs.typos
+              edge-pkgs.go-task
             ];
           };
       });