match: check if an object is a baseset using `isascending` instead of `set`

The `set()` method is going away.

mercurial/revset.py

@@ -2064,7 +2064,7 b' def match(ui, spec, repo=None):'
         tree = findaliases(ui, tree)
     weight, tree = optimize(tree, True)
     def mfunc(repo, subset):
-        if util.safehasattr(subset, 'set'):
+        if util.safehasattr(subset, 'isascending'):
             result = getset(repo, subset, tree)
         else:
             result = getset(repo, baseset(subset), tree)