#! /usr/bin/env python

 import sys

 import os

 if len(sys.argv)>1 and sys.argv[1] in ["-h","--help"]:

     print """

 This utility just prints the length of the longest path

 in the revision graph from revison 0 to the current one.

 """

     exit(0)

 plist = os.popen("hg parents --template='{rev}\n'").readlines()

 if len(plist)>1:

     print "You are in the process of merging"

     exit(1)

 PAR = int(plist[0])

 f = os.popen("hg log -r 0:tip --template='{rev} {parents}\n'").readlines()

 REV = -1

 lengths=[]

 for l in f:

     REV+=1

     s = l.split()

     rev = int(s[0])

     if REV != rev:

         print "Something is seriously wrong"

         exit(1)

     if len(s) == 1:

         par1 = par2 = rev - 1

     elif len(s) == 2:

         par1 = par2 = int(s[1].split(":")[0])

     else:

         par1 = int(s[1].split(":")[0])

         par2 = int(s[2].split(":")[0])

     if rev == 0:

         lengths.append(0)

     else:

         lengths.append(max(lengths[par1],lengths[par2])+1)

 print lengths[PAR]