Derivation in seperate file

flake.nix

@@ -7,31 +7,8 @@
   flake-utils.lib.eachDefaultSystem ( system:
   let pkgs = import nixpkgs { inherit system; };
   in{
-    packages = rec {
-      default = pkgs.stdenvNoCC.mkDerivation rec {
-        pname   = "irs";
-        version = "0.2";
-
-        src = ./src;
-
-        buildInputs = with pkgs; [
-          coreutils
-          scdoc
-        ];
-
-        buildPhase = ''
-          for page in $(find manpages -type f); do
-            scdoc < $page > $(basename $page .scd)
-          done
-        '';
-
-        installPhase = ''
-          mkdir -p $out/{share/man/man1,bin,share/zsh/site-functions}
-          cp bin/* $out/bin/
-          cp completions/* $out/share/zsh/site-functions/
-          cp *.1 $out/share/man/man1/
-        '';
-      };
+    packages = {
+      default = pkgs.callPackage ./default.nix {};
     };
   });
 }