fetch-mutable-files: add file submodule

modules/home-manager/fetch-mutable-files.nix

@@ -2,12 +2,47 @@
 
 let
   cfg = config.home.mutableFiles;
-  file = { config, name, ... }: {
+  file = baseDir: { config, name, ... }: {
+    options = {
+      url = lib.mkOption {
+        type = lib.types.str;
+        description = lib.mkDoc ''
+          The URL of the file to be fetched.
+        '';
+        example = "https://github.com/foo-dogsquared/dotfiles.git";
+      };
+
+      path = lib.mkOption {
+        type = lib.types.str;
+        description = lib.mkDoc ''
+          Output path of the resource relative to ${baseDir}.
+        '';
+        default = name;
+        apply = p:
+          if lib.hasPrefix "/" p then p else "${baseDir}/${p}";
+      };
+
+      type = lib.mkOption {
+        type = lib.types.enum [ "git" "fetch" ];
+        description = lib.mkDoc ''
+          Type that configures the behavior for fetching the URL.
+
+          This accept only certain keywords.
+
+          - For `fetch`, the file will be fetched with `curl`.
+          - For `git`, it will be fetched with `git clone`.
+
+          The default type is `fetch`.
+        '';
+        default = "fetch";
+        example = "git";
+      };
+    };
   };
 in
 {
   options.home.mutableFile = lib.mkOption {
-    type = with lib.types; attrsOf (submodule file);
+    type = with lib.types; attrsOf (submodule (file config.home.homeDirectory));
     default = { };
     description = lib.mkDoc ''
       An attribute set of mutable files and directories to be fetched into the