527 def _updatedefaultdest(repo, subset, x):

   528     # ``_updatedefaultdest()``

   529 

   530     # default destination for update.

   531     # # XXX: Currently private because I expect the signature to change.

   532     # # XXX: - taking rev as arguments,

   533     # # XXX: - bailing out in case of ambiguity vs returning all data.

   534     getargs(x, 0, 0, _("_updatedefaultdest takes no arguments"))

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

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

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

   538     node = None

   539     wc = repo[None]

   540     p1 = wc.p1()

   541     try:

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

   543     except error.RepoLookupError:

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

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

   546         else:

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

   548 

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

   550         # allow updating to successors

   551         successors = obsmod.successorssets(repo, p1.node())

   552 

   553         # behavior of certain cases is as follows,

   554         #

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

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

   557         #     (i.e. 'tip')

   558         #

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

   560         # is no conflict

   561         #

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

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

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

   565 

   566         if successors:

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

   568             # and the usual case (len = 1)

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

   570 

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

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

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

   574     return subset & baseset([repo[node].rev()])

   575 

  2214     "_updatedefaultdest": _updatedefaultdest,