Comment 1 for bug 86940

I think this is totally bogus. find_ids_across_trees should only return None if its input is None.

Functions and methods that get an empty list should treat it as an empty list. I think you want to treat user input of the empty list as meaning wildcard, but that should be done as part of user input parsing, and perhaps not in all cases.

Treating [] differently from all other lists is a bogosity that does not belong in the Bazaar API, e.g. WT.revert