wireproto: fix decodelist to properly return empty list
Needed by tests for next patch introducing known().
debug: add debugwireargs to test argument passing over the wire
Tests argument passing locally, via HTTP, and via SSH. This is mainly preparation
for the next patch.
merge: avoid unlinking destination of merge when case changes (
issue2715)
changegroupsubset: simplify prune
Ancestors of nodes linked to commonrevs can be expected to be linked
to commonrevs. Walking graphs of each revlog looking for rare/nonexistent outliers is overkill.