improve the sourcing mapping.

pkgs/default.nix

@@ -5,7 +5,7 @@
   pkgs            ? import (hostPkgs.nix-update-source.fetch ./pkgs.json).src {}
 
 , # fetcher alias for the remaining arguments
-  fetched         ? (s: (pkgs.nix-update-source.fetch s).src)
+  fetched         ? s: (pkgs.nix-update-source.fetch s).src
 
 , #source overrides: core nrm components
   aml-src         ? fetched aml/pin.json
@@ -21,9 +21,9 @@
 , lammps-src      ? fetched lammps/pin.json
 
 , #source overrides :tooling
-  repoquality-src ? fetched repoquality/pin.json,
-  argotk-src      ? fetched argotk/pin.json,
-  argonix-src     ? fetched argonix/pin.json,
+  argotk-src       ? builtins.fetchGit {inherit (fetched argotk/pin.json) url rev;},
+  repoquality-src  ? builtins.fetchGit {inherit (fetched repoquality/pin.json) url rev;},
+  argonix-src      ? builtins.fetchGit {inherit (fetched argonix/pin.json) url rev;},
 }:
 let
   callPackage = pkgs.lib.callPackageWith (pkgs // argopkgs);
@@ -62,9 +62,9 @@ let
                       inherit (panhandle-src) url rev; })) {};
 
         #argo tools
-        argotk = (self.callCabal2nix "argotk" (builtins.fetchGit {inherit (argotk-src) url rev;})) {};
-        argonix = (self.callCabal2nix "argonix" (builtins.fetchGit {inherit (argonix-src) url rev;})) {};
-        repoquality = (self.callCabal2nix "repoquality" (builtins.fetchGit {inherit (repoquality-src) url rev;})) {};
+        argotk = (self.callCabal2nix "argotk" argotk-src) {};
+        argonix = (self.callCabal2nix "argonix" argonix-src) {};
+        repoquality = (self.callCabal2nix "repoquality" repoquality-src) {};
       };
     };