revset: remove order information from tree (API) Keeping `order` in tree makes AST operation harder. And there could be invalid cases if trees could be generated and compounded freely, like: SetA(order=define) & SetB(order=define) ^^^^^^ couldn't be satisfied This patch changes the code to calculate order on the fly, during tree traversal. Optimization of reordering `and` arguments is preserved by introducing a new internal operation `flipand`. .. api:: revset.stringset() now takes 'order' as the last argument. Differential Revision: https://phab.mercurial-scm.org/D451