216 def finddepths(nodes, pfunc):

   217     visit = list(nodes)

   218     rootpl = [nullrev, nullrev]

   219     depth = {}

   220     while visit:

   221         vertex = visit[-1]

   222         pl = pfunc(vertex)

   223         if not pl or pl == rootpl:

   224             depth[vertex] = 0

   225             visit.pop()

   226         else:

   227             for p in pl:

   228                 if p != nullrev and p not in depth:

   229                     visit.append(p)

   230             if visit[-1] == vertex:

   231                 dp = [depth[p] for p in pl if p != nullrev]

   232                 if dp:

   233                     depth[vertex] = max(dp) + 1

   234                 else:

   235                     depth[vertex] = 0

   236                 visit.pop()

   237     return depth

   238 

   239 def ancestor(a, b, pfunc):

   240     xs = ancestors(pfunc, a, b)

   241     y = genericancestor(a, b, pfunc)

   242     if y == -1:

   243         y = None

   244     if not xs:

   245         if y is None:

   246             return None

   247         print xs, y

   248         raise error.RepoError('ancestors disagree on whether a gca exists')

   249     elif y is None:

   250         print xs, y

   251         raise error.RepoError('ancestors disagree on whether a gca exists')

   252     if y in xs:

   253         return y

   254     xds = finddepths(xs, pfunc)

   255     xds = [ds[x] for x in xs]

   256     yd = finddepths([y], pfunc)[y]

   257     if len([xd != yd for xd in xds]) > 0:

   258         raise error.RepoError('ancestor depths do not match')

   259     return xs.pop()

   260