topgrade: add module (#1924)

modules/programs/topgrade.nix

@@ -0,0 +1,60 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.programs.topgrade;
+
+  tomlFormat = pkgs.formats.toml { };
+
+in {
+
+  meta.maintainers = [ hm.maintainers.msfjarvis ];
+
+  options.programs.topgrade = {
+    enable = mkEnableOption "topgrade";
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.topgrade;
+      defaultText = literalExample "pkgs.topgrade";
+      description = "The package to use for the topgrade binary.";
+    };
+
+    settings = mkOption {
+      type = tomlFormat.type;
+      default = { };
+      defaultText = literalExample "{ }";
+      example = literalExample ''
+        {
+          assume_yes = true;
+          disable = [
+            "flutter"
+            "node"
+          ];
+          set_title = false;
+          cleanup = true;
+          commands = {
+            "Run garbage collection on Nix store" = "nix-collect-garbage";
+          };
+        }
+      '';
+      description = ''
+        Configuration written to
+        <filename>~/.config/topgrade.toml</filename>.
+        </para><para>
+        See <link xlink:href="https://github.com/r-darwish/topgrade/wiki/Step-list" /> for the full list
+        of options.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    home.packages = [ cfg.package ];
+
+    xdg.configFile."topgrade.toml" = mkIf (cfg.settings != { }) {
+      source = tomlFormat.generate "topgrade-config" cfg.settings;
+    };
+  };
+}