revset: allow bypassing alias expansion

For internal usage of revset queries, we don't want aliases breaking things.

mercurial/revset.py

@@ -1019,7 +1019,8 b' def match(ui, spec):'
     tree, pos = parse(spec)
     if (pos != len(spec)):
         raise error.ParseError(_("invalid token"), pos)
-    tree = findaliases(ui, tree)
+    if ui:
+        tree = findaliases(ui, tree)
     weight, tree = optimize(tree, True)
     def mfunc(repo, subset):
         return getset(repo, subset, tree)