--- a/mercurial/ancestor.py	Sat Mar 29 12:39:47 2008 -0500
+++ b/mercurial/ancestor.py	Sat Mar 29 12:39:47 2008 -0500
@@ -81,43 +81,3 @@
                 gx = x.next()
     except StopIteration:
         return None
-
-def symmetricdifference(a, b, pfunc):
-    """symmetric difference of the sets of ancestors of a and b
-
-    I.e. revisions that are ancestors of a or b, but not both.
-    """
-    # basic idea:
-    # - mark a and b with different sides
-    # - if a parent's children are all on the same side, the parent is
-    #   on that side, otherwise it is on no side
-    # - walk the graph in topological order with the help of a heap;
-    #   - add unseen parents to side map
-    #   - clear side of any parent that has children on different sides
-    #   - track number of unvisited nodes that might still be on a side
-    #   - quit when interesting nodes is zero
-    if a == b:
-        return [a]
-
-    side = {a: -1, b: 1}
-    visit = [-a, -b]
-    heapq.heapify(visit)
-    interesting = len(visit)
-
-    while interesting:
-        r = -heapq.heappop(visit)
-        if side[r]:
-            interesting -= 1
-        for p in pfunc(r):
-            if p not in side:
-                # first time we see p; add it to visit
-                side[p] = side[r]
-                if side[p]:
-                    interesting += 1
-                heapq.heappush(visit, -p)
-            elif side[p] and side[p] != side[r]:
-                # p was interesting but now we know better
-                side[p] = 0
-                interesting -= 1
-
-    return [r for r in side if side[r]]