nixos/systemd: allow disabling the path default for services (#482045)

nixos/lib/systemd-lib.nix

@@ -688,17 +688,19 @@ rec {
       };
     };
 
-  stage2ServiceConfig = {
+  stage2ServiceConfig =
-    imports = [ serviceConfig ];
+    { config, ... }:
-    # Default path for systemd services. Should be quite minimal.
+    {
-    config.path = mkAfter [
+      imports = [ serviceConfig ];
-      pkgs.coreutils
+      # Default path for systemd services. Should be quite minimal.
-      pkgs.findutils
+      config.path = mkIf config.enableDefaultPath (mkAfter [
-      pkgs.gnugrep
+        pkgs.coreutils
-      pkgs.gnused
+        pkgs.findutils
-      systemd
+        pkgs.gnugrep
-    ];
+        pkgs.gnused
-  };
+        systemd
+      ]);
+    };
 
   stage1ServiceConfig = serviceConfig;
 

nixos/lib/systemd-unit-options.nix

@@ -379,6 +379,14 @@ rec {
           '';
         };
 
+        enableDefaultPath = mkOption {
+          default = true;
+          type = types.bool;
+          description = ''
+            Whether to append a minimal default {env}`PATH` environment variable to the service, containing common system utilities.
+          '';
+        };
+
         serviceConfig = mkOption {
           default = { };
           example = {