revset: added sort methods to generatorsets

Method needed to propagate sort calls amongst lazy structures.
The generated list (stored in the object) is sorted.

If the generated list did not contain all elements from the generator, we
take care of that before sorting the list.

mercurial/revset.py

@@ -2348,6 +2348,7 b' class generatorset(object):'
         self._cache = {}
         self._genlist = baseset([])
         self._iterated = False
+        self._finished = False
 
     def __contains__(self, x):
         if x in self._cache:
@@ -2357,6 +2358,7 b' class generatorset(object):'
             if l == x:
                 return True
 
+        self._finished = True
         self._cache[x] = False
         return False
 
@@ -2372,9 +2374,18 b' class generatorset(object):'
             self._genlist.append(item)
             yield item
 
+        self._finished = True
+
     def set(self):
         return self
 
+    def sort(self, reverse=False):
+        # Basic implementation to be changed in future patches
+        if not self._finished:
+            for i in self:
+                continue
+        self._genlist.sort(reverse=reverse)
+
 class ascgeneratorset(generatorset):
     """ Same structure as generatorset but stops iterating after it goes past
     the value when asked for membership and the element is not contained