# destutil.py - Mercurial utility function for command destination

#

#  Copyright Matt Mackall <mpm@selenic.com> and other

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from .i18n import _

from . import (

    error,

    util,

    obsolete,

)

def destupdate(repo):

    """destination for bare update operation

    """

    # Here is where we should consider bookmarks, divergent bookmarks, and tip

    # of current branch; but currently we are only checking the branch tips.

    node = None

    wc = repo[None]

    p1 = wc.p1()

    try:

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

    except error.RepoLookupError:

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

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

        else:

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

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

        # allow updating to successors

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

        # behavior of certain cases is as follows,

        #

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

        #     is currently done when there are more than one head

        #     (i.e. 'tip')

        #

        # replaced changesets: same as divergent except we know there

        # is no conflict

        #

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

        #     consider updating to the first non-obsolete parent,

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

        if successors:

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

            # and the usual case (len = 1)

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

            # get the max revision for the given successors set,

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

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

    return repo[node].rev()