revset: flatten chained 'list' operations (aka function args) (issue5072) Internal _matchfiles() function can take bunch of arguments, which would lead to a maximum recursion depth error. This patch avoids the excessive stack use by flattening 'list' nodes beforehand. Since getlist() no longer takes a nested 'list' nodes, _parsealiasdecl() also needs to flatten argument list, "aliasname($1, $2, ...)".