difftool: make --gui, --tool and --extcmd mutually exclusive

diff --git a/transport-helper.c b/transport-helper.c
index 143ca008c8f20384c8c4636e5372817946e66e14..7213fa0d320284e318c7895cc0915ef556ac4f6d 100644 (file)
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -1105,6 +1105,7 @@ static struct ref *get_refs_list(struct transport *transport, int for_push,
 }
 
 static struct transport_vtable vtable = {
+       0,
        set_helper_option,
        get_refs_list,
        fetch,