"""

        from kallithea.lib.vcs.backends.base import BaseChangeset

        if cs_cache is None:

            cs_cache = EmptyChangeset()

            # use no-cache version here

            scm_repo = self.scm_instance_no_cache()

            if scm_repo:

                cs_cache = scm_repo.get_changeset()

        if isinstance(cs_cache, BaseChangeset):

            cs_cache = cs_cache.__json__()

        if (not self.changeset_cache or cs_cache['raw_id'] != self.changeset_cache['raw_id']):

            _default = datetime.datetime.fromtimestamp(0)

            last_change = cs_cache.get('date') or _default

            log.debug('updated repo %s with new cs cache %s',

                      self.repo_name, cs_cache)

            self.updated_on = last_change

            self.changeset_cache = cs_cache

            Session().add(self)

            Session().commit()

        else:

            log.debug('changeset_cache for %s already up to date with %s',

                      self.repo_name, cs_cache['raw_id'])

    @property

    def tip(self):

        return self.get_changeset('tip')

    @property

    def author(self):

        return self.tip.author

    @property

    def last_change(self):

        return self.scm_instance.last_change

    def get_comments(self, revisions=None):

        """

        Returns comments for this repository grouped by revisions

        :param revisions: filter query by revisions only

        """

        cmts = ChangesetComment.query() \

            .filter(ChangesetComment.repo == self)

        if revisions is not None:

            if not revisions:

                return {} # don't use sql 'in' on empty set

            cmts = cmts.filter(ChangesetComment.revision.in_(revisions))

        grouped = collections.defaultdict(list)

        for cmt in cmts.all():

            grouped[cmt.revision].append(cmt)

        return grouped

    def statuses(self, revisions):

        """

        Returns statuses for this repository.

        PRs without any votes do _not_ show up as unreviewed.

        :param revisions: list of revisions to get statuses for

        """

        if not revisions:

            return {}

        statuses = ChangesetStatus.query() \

            .filter(ChangesetStatus.repo == self) \

            .filter(ChangesetStatus.version == 0) \

            .filter(ChangesetStatus.revision.in_(revisions))

        grouped = {}

        for stat in statuses.all():

            pr_id = pr_nice_id = pr_repo = None

            if stat.pull_request:

                pr_id = stat.pull_request.pull_request_id

                pr_nice_id = PullRequest.make_nice_id(pr_id)

                pr_repo = stat.pull_request.other_repo.repo_name

            grouped[stat.revision] = [str(stat.status), stat.status_lbl,

                                      pr_id, pr_repo, pr_nice_id,

                                      stat.author]

        return grouped

    def _repo_size(self):

        from kallithea.lib import helpers as h

        log.debug('calculating repository size...')

        return h.format_byte_size(self.scm_instance.size)

    #==========================================================================

    # SCM CACHE INSTANCE

    #==========================================================================

    def set_invalidate(self):

        """

        Mark caches of this repo as invalid.

        """

        CacheInvalidation.set_invalidate(self.repo_name)

    @property

    def scm_instance(self):

    def scm_instance_cached(self, valid_cache_keys=None):

        @cache_region('long_term', 'scm_instance_cached')

        def _c(repo_name): # repo_name is just for the cache key

            log.debug('Creating new %s scm_instance and populating cache', repo_name)

            return self.scm_instance_no_cache()

        rn = self.repo_name

        valid = CacheInvalidation.test_and_set_valid(rn, None, valid_cache_keys=valid_cache_keys)

        if not valid:

            log.debug('Cache for %s invalidated, getting new object', rn)

            region_invalidate(_c, None, 'scm_instance_cached', rn)

        else:

            log.debug('Trying to get scm_instance of %s from cache', rn)

        return _c(rn)

    def scm_instance_no_cache(self):

        repo_full_path = safe_str(self.repo_full_path)

        alias = get_scm(repo_full_path)[0]

        log.debug('Creating instance of %s repository from %s',

                  alias, self.repo_full_path)

        backend = get_backend(alias)

        if alias == 'hg':

            repo = backend(repo_full_path, create=False,

                           baseui=self._ui)

        else:

            repo = backend(repo_full_path, create=False)

        return repo

    def __json__(self):

        return dict(landing_rev = self.landing_rev)

class RepoGroup(Base, BaseModel):

    __tablename__ = 'groups'

    __table_args__ = (

        UniqueConstraint('group_name', 'group_parent_id'),

        CheckConstraint('group_id != group_parent_id'),

        _table_args_default_dict,

    )

    __mapper_args__ = {'order_by': 'group_name'}

    SEP = ' » '

    group_id = Column(Integer(), unique=True, primary_key=True)

    group_name = Column(Unicode(255), nullable=False, unique=True)

    group_parent_id = Column(Integer(), ForeignKey('groups.group_id'), nullable=True)

    group_description = Column(Unicode(10000), nullable=False)

    enable_locking = Column(Boolean(), nullable=False, default=False)

    user_id = Column(Integer(), ForeignKey('users.user_id'), nullable=False)

    created_on = Column(DateTime(timezone=False), nullable=False, default=datetime.datetime.now)

    repo_group_to_perm = relationship('UserRepoGroupToPerm', cascade='all', order_by='UserRepoGroupToPerm.group_to_perm_id')

    users_group_to_perm = relationship('UserGroupRepoGroupToPerm', cascade='all')

    parent_group = relationship('RepoGroup', remote_side=group_id)

    user = relationship('User')

    def __init__(self, group_name='', parent_group=None):

        self.group_name = group_name

        self.parent_group = parent_group

    def __unicode__(self):

        return u"<%s('id:%s:%s')>" % (self.__class__.__name__, self.group_id,

                                      self.group_name)

    @classmethod

    def _generate_choice(cls, repo_group):

        """Return tuple with group_id and name as html literal"""

        from webhelpers.html import literal

        if repo_group is None:

            return (-1, u'-- %s --' % _('top level'))

        return repo_group.group_id, literal(cls.SEP.join(repo_group.full_path_splitted))

    @classmethod

    def groups_choices(cls, groups):

        """Return tuples with group_id and name as html literal."""

        return sorted((cls._generate_choice(g) for g in groups),

                      key=lambda c: c[1].split(cls.SEP))

    @classmethod

    def url_sep(cls):

        return URL_SEP

    @classmethod

    def get_by_group_name(cls, group_name, cache=False, case_insensitive=False):

        if case_insensitive:

            gr = cls.query() \

                .filter(func.lower(cls.group_name) == func.lower(group_name))

        else:

            gr = cls.query() \

                .filter(cls.group_name == group_name)

        if cache:

            gr = gr.options(FromCache(

                            "sql_cache_short",

                            "get_group_%s" % _hash_key(group_name)