feat(pkgs): add genericBinWrapper & mullvadExcludeWrapper

These allow creating wrapped packages that passthrough their arguments, so
`.override` can still be called on them with same arguments.

flake.nix

@@ -68,6 +68,11 @@
         deconz = final: prev: {
           deconz = final.qt5.callPackage ./pkgs/deconz { };
         };
+        wrappers = final: prev: {
+          genericBinWrapper = final.callPackage ./pkgs/generic-bin-wrapper { };
+          mullvadExcludeWrapper =
+            final.callPackage ./pkgs/mullvad-exclude-wrapper { };
+        };
       };
       nixosModules = {
         flakeDefaults = import ./modules/flakeDefaults.nix;
@@ -80,7 +85,13 @@
       };
       systemDefaults = {
         modules = [ nixosModules.flakeDefaults agenix.nixosModules.default ];
-        overlays = with overlays; [ unstable nur.overlay neovim deconz ];
+        overlays = with overlays; [
+          unstable
+          nur.overlay
+          neovim
+          deconz
+          wrappers
+        ];
       };
       lib = rec {
         createSystem = hostName:

pkgs/generic-bin-wrapper/default.nix

@@ -0,0 +1,32 @@
+{ stdenv, callPackage }:
+
+{ package # pkg must contain $out/bin with executables within.
+, binPath ?
+  "bin/${package.meta.mainProgram or package.pname}" # path to look for binary
+, wrapper # wrapper must contain @EXECUTABLE@ as a placeholder for the binary to run.
+}:
+
+# pass through all arguments to wrapped package to allow overriding
+# arguments in wrapped package
+callPackage (args:
+  stdenv.mkDerivation {
+    name = "${package.name}-wrapped";
+    inherit (package) version;
+    src = package.override args;
+    dontUnpack = true;
+
+    # inherit passthru
+    inherit (package) passthru;
+
+    installPhase = ''
+      local executable=$out/${binPath}
+      install -D ${wrapper} "$executable"
+      substituteInPlace "$executable" --subst-var-by EXECUTABLE "$f"
+
+      # Symlink the share directory so that .desktop files and such continue to work.
+      if [[ -d $src/share ]]
+      then
+        ln -s $src/share $out/share
+      fi
+    '';
+  }) { }

pkgs/mullvad-exclude-wrapper/default.nix

@@ -0,0 +1,7 @@
+{ writeShellScript, genericBinWrapper, mullvad-vpn }:
+args:
+let
+  wrapper = writeShellScript "mullvad-exclude" ''
+    ${mullvad-vpn}/bin/mullvad-exclude "@EXECUTABLE@" "$@"
+  '';
+in genericBinWrapper (args // { inherit wrapper; })