revset: force ascending order for baseset initialized from a set

It is possible to initialize a baseset directly from a set object. However, in
this case the iteration order was inherited from the set. Set have undefined
iteration order (especially cpython and pypy will have different one) so we
should not rely on it anywhere.

Therefor we declare the baseset "ascending" to enforce a consistent iteration
order. The sorting is done lazily by the baseset class and should have no
performance impact when it does not matter.

This makes test-revset.t pass with pypy.

mercurial/revset.py

@@ -2798,13 +2798,15 b' class baseset(abstractsmartset):'
         datarepr: a tuple of (format, obj, ...), a function or an object that
                   provides a printable representation of the given data.
         """
+        self._ascending = None
         if not isinstance(data, list):
             if isinstance(data, set):
                 self._set = data
+                # set has no order we pick one for stability purpose
+                self._ascending = True
             data = list(data)
         self._list = data
         self._datarepr = datarepr
-        self._ascending = None
 
     @util.propertycache
     def _set(self):