173         def expand(e1, e2, a1, a2):

   173         def expand(list, map):

   174             ne = []

   174             a = []

   175             for n in e1:

   175             while list:

   176                 (p1, p2) = self.parents(n)

   176                 n = list.pop(0)

   177                 if p1 in a2: return p1

   177                 map[n] = 1

   178                 if p2 in a2: return p2

   178                 yield n

   179                 if p1 != nullid and p1 not in a1:

   179                 for p in self.parents(n):

   180                     a1[p1] = 1

   180                     if p != nullid and p not in map:

   181                     ne.append(p1)

   181                         list.append(p)

   182                 if p2 != nullid and p2 not in a1:

   182             yield nullid

   183                     a1[p2] = 1

   183 

   184                     ne.append(p2)

   184         amap = {}

   185             return expand(e2, ne, a2, a1)

   185         bmap = {}

   186         return expand([a], [b], {a:1}, {b:1})

   186         ag = expand([a], amap)

   187         bg = expand([b], bmap)

   188         adone = bdone = 0

   189 

   190         while not adone or not bdone:

   191             if not adone:

   192                 an = ag.next()

   193                 if an == nullid:

   194                     adone = 1

   195                 elif an in bmap:

   196                     return an

   197             if not bdone:

   198                 bn = bg.next()

   199                 if bn == nullid:

   200                     bdone = 1

   201                 elif bn in amap:

   202                     return bn

   203 

   204         return nullid