988             # Here is where we should consider bookmarks, divergent bookmarks,

   987             nodes = list(repo.set('_updatedefaultdest()'))

   989             # foreground changesets (successors), and tip of current branch;

   988             if nodes:

   990             # but currently we are only checking the branch tips.

   989                 node = nodes[0].node()

   991             try:

   990                 if p1.obsolete() and not p1.children():

   992                 node = repo.branchtip(wc.branch())

   993             except errormod.RepoLookupError:

   994                 if wc.branch() == 'default': # no default branch!

   995                     node = repo.lookup('tip') # update to tip

   996                 else:

   997                     raise util.Abort(_("branch %s not found") % wc.branch())

   998 

   999             if p1.obsolete() and not p1.children():

  1000                 # allow updating to successors

  1001                 successors = obsolete.successorssets(repo, p1.node())

  1002 

  1003                 # behavior of certain cases is as follows,

  1004                 #

  1005                 # divergent changesets: update to highest rev, similar to what

  1006                 #     is currently done when there are more than one head

  1007                 #     (i.e. 'tip')

  1008                 #

  1009                 # replaced changesets: same as divergent except we know there

  1010                 # is no conflict

  1011                 #

  1012                 # pruned changeset: no update is done; though, we could

  1013                 #     consider updating to the first non-obsolete parent,

  1014                 #     similar to what is current done for 'hg prune'

  1015 

  1016                 if successors:

  1017                     # flatten the list here handles both divergent (len > 1)

  1018                     # and the usual case (len = 1)

  1019                     successors = [n for sub in successors for n in sub]

  1020 

  1021                     # get the max revision for the given successors set,

  1022                     # i.e. the 'tip' of a set

  1023                     node = repo.revs('max(%ln)', successors).first()