modules/dependencies: introduce top-level (internal) __depPackages option

modules/dependencies.nix

@@ -5,9 +5,71 @@
   ...
 }:
 let
+  inherit (lib) types;
+
   cfg = config.dependencies;
 
-  packages = {
+  mkDependencyOption = name: properties: {
+    enable = lib.mkEnableOption "Add ${name} to dependencies.";
+
+    package =
+      lib.mkPackageOption pkgs name properties
+      # Handle example manually so that we can embed the original attr-path within
+      # the literalExpression object. This simplifies testing the examples.
+      // lib.optionalAttrs (properties.example != null) {
+        example =
+          if properties.example._type or null == "literalExpression" then
+            properties.example
+          else
+            rec {
+              _type = "literalExpression";
+              text = "pkgs.${lib.showAttrPath path}";
+              path = lib.toList properties.example;
+            };
+      };
+  };
+in
+{
+  options = {
+    __depPackages = lib.mkOption {
+      type = types.attrsOf (
+        types.submodule {
+          options = {
+            default = lib.mkOption {
+              type = with types; either str (listOf str);
+              description = ''
+                Default name (or path) for this package.
+              '';
+              example = "git";
+            };
+
+            example = lib.mkOption {
+              type = with types; nullOr str;
+              description = ''
+                Example of another package to use instead of the default.
+              '';
+              example = "gitMinimal";
+              default = null;
+            };
+          };
+        }
+      );
+      default = { };
+      internal = true;
+      visible = false;
+    };
+
+    dependencies = lib.mapAttrs mkDependencyOption config.__depPackages;
+  };
+
+  config = {
+    extraPackages = lib.pipe cfg [
+      builtins.attrValues
+      (builtins.filter (p: p.enable))
+      (builtins.map (p: p.package))
+    ];
+
+    __depPackages = {
       bat.default = "bat";
       codeium.default = "codeium";
       coreutils = {
@@ -67,35 +129,5 @@ let
       yq.default = "yq";
       zk.default = "zk";
     };
-
-  mkDependencyOption = name: properties: {
-    enable = lib.mkEnableOption "Add ${name} to dependencies.";
-
-    package =
-      lib.mkPackageOption pkgs name properties
-      # Handle example manually so that we can embed the original attr-path within
-      # the literalExpression object. This simplifies testing the examples.
-      // lib.optionalAttrs (properties ? example) {
-        example =
-          if properties.example._type or null == "literalExpression" then
-            properties.example
-          else
-            rec {
-              _type = "literalExpression";
-              text = "pkgs.${lib.showAttrPath path}";
-              path = lib.toList properties.example;
-            };
-      };
-  };
-in
-{
-  options.dependencies = lib.mapAttrs mkDependencyOption packages;
-
-  config = {
-    extraPackages = lib.pipe cfg [
-      builtins.attrValues
-      (builtins.filter (p: p.enable))
-      (builtins.map (p: p.package))
-    ];
   };
 }