Merge pull request #176456 from klemensn/nixos-rebuild-synopsis

nixos-rebuild: Accept only one argument

pkgs/os-specific/linux/nixos-rebuild/nixos-rebuild.sh

@@ -49,6 +49,8 @@ while [ "$#" -gt 0 ]; do
         ;;
       switch|boot|test|build|edit|dry-build|dry-run|dry-activate|build-vm|build-vm-with-bootloader)
         if [ "$i" = dry-run ]; then i=dry-build; fi
+        # exactly one action mandatory, bail out if multiple are given
+        if [ -n "$action" ]; then showSyntax; fi
         action="$i"
         ;;
       --install-grub)