def scm_instance(self):

        import kallithea

        full_cache = str2bool(kallithea.CONFIG.get('vcs_full_cache'))

        if full_cache:

            return self.scm_instance_cached()

        return self.__get_instance()

    def scm_instance_cached(self, valid_cache_keys=None):

        @cache_region('long_term')

        def _c(repo_name):

            return self.__get_instance()

        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, rn)

        else:

            log.debug('Getting scm_instance of %s from cache', rn)

        return _c(rn)

    def __get_instance(self):

        repo_full_path = self.repo_full_path

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

                  alias, repo_full_path)

        backend = get_backend(alias)

        if alias == 'hg':

            repo = backend(safe_str(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'),

        {'extend_existing': True, 'mysql_engine': 'InnoDB',

         'mysql_charset': 'utf8', 'sqlite_autoincrement': True},

    )

    __mapper_args__ = {'order_by': 'group_name'}

            for k, v in baseui.configitems('hooks'):

                baseui.setconfig('hooks', k, None)

            repo = backend(repo_path, create=True, src_url=clone_uri, baseui=baseui)

        elif repo_type == 'git':

            repo = backend(repo_path, create=True, src_url=clone_uri, bare=True)

            # add kallithea hook into this repo

            ScmModel().install_git_hooks(repo=repo)

        else:

            raise Exception('Not supported repo_type %s expected hg/git' % repo_type)

        log.debug('Created repo %s with %s backend',

                  safe_unicode(repo_name), safe_unicode(repo_type))

        return repo

    def _rename_filesystem_repo(self, old, new):

        """

        renames repository on filesystem

        :param old: old name

        :param new: new name

        """

        log.info('renaming repo from %s to %s', old, new)

        if os.path.isdir(new_path):

            raise Exception(

                'Was trying to rename to already existing dir %s' % new_path

            )

        shutil.move(old_path, new_path)

    def _delete_filesystem_repo(self, repo):

        """

        removes repo from filesystem, the removal is actually done by

        renaming dir to a 'rm__*' prefix which Kallithea will skip.

        It can be undeleted later by reverting the rename.

        :param repo: repo object

        """

        log.info("Removing %s", rm_path)

        _now = datetime.now()

        _ms = str(_now.microsecond).rjust(6, '0')

        _d = 'rm__%s__%s' % (_now.strftime('%Y%m%d_%H%M%S_' + _ms),

                             repo.just_name)

        if repo.group:

            args = repo.group.full_path_splitted + [_d]

            _d = os.path.join(*args)