add comment about msgpack >= 0.6.1 features for later

src/borg/helpers/msgpack.py

@@ -75,6 +75,11 @@ def pack(o, stream, *, use_bin_type=False, encoding=None, unicode_errors=None, *
         raise PackException(e)
 
 
+# Note: after requiring msgpack >= 0.6.1 we can remove the max_*_len args and
+#       rely on msgpack auto-computing DoS-safe max values from len(data) for
+#       unpack(data) or from max_buffer_len for Unpacker(max_buffer_len=N).
+#       maybe we can also use that to simplify get_limited_unpacker().
+
 class Unpacker(mp_Unpacker):
     def __init__(self, file_like=None, *, read_size=0, use_list=True, raw=True,
                  object_hook=None, object_pairs_hook=None, list_hook=None,