updated for version 7.3.445
Problem:    Can't properly escape commands for cmd.exe.
Solution:   Default 'shellxquote' to '('.  Append ')' to make '(command)'.
            No need to use "/s" for 'shellcmdflag'.
diff --git a/src/misc2.c b/src/misc2.c
index 00d1ff4..fc38cd0 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -3230,7 +3230,11 @@
 	    {
 		STRCPY(ncmd, p_sxq);
 		STRCAT(ncmd, cmd);
-		STRCAT(ncmd, p_sxq);
+		/* When 'shellxquote' is ( append ).
+		 * When 'shellxquote' is "( append )". */
+		STRCAT(ncmd, STRCMP(p_sxq, "(") == 0 ? (char_u *)")"
+			   : STRCMP(p_sxq, "\"(") == 0 ? (char_u *)")\""
+			   : p_sxq);
 		retval = mch_call_shell(ncmd, opt);
 		vim_free(ncmd);
 	    }