repo_update_list=None):

        self.indexname = indexname

        self.index_location = index_location

        if not index_location:

            raise Exception('You have to provide index location')

        self.repo_location = repo_location

        if not repo_location:

            raise Exception('You have to provide repositories location')

        self.repo_paths = ScmModel().repo_scan(self.repo_location)

        # filter repo list

        if repo_list:

            # Fix non-ascii repo names to unicode

            repo_list = set(safe_unicode(repo_name) for repo_name in repo_list)

            self.filtered_repo_paths = {}

            for repo_name, repo in self.repo_paths.items():

                if repo_name in repo_list:

                    self.filtered_repo_paths[repo_name] = repo

            self.repo_paths = self.filtered_repo_paths

        # filter update repo list

        self.filtered_repo_update_paths = {}

        if repo_update_list:

            self.filtered_repo_update_paths = {}

            for repo_name, repo in self.repo_paths.items():

                if repo_name in repo_update_list:

                    self.filtered_repo_update_paths[repo_name] = repo

            self.repo_paths = self.filtered_repo_update_paths

        self.initial = True

        if not os.path.isdir(self.index_location):

            os.makedirs(self.index_location)

            log.info('Cannot run incremental index since it does not '

                     'yet exist - running full build')

        elif not exists_in(self.index_location, IDX_NAME):

            log.info('Running full index build, as the file content '

                     'index does not exist')

        elif not exists_in(self.index_location, CHGSET_IDX_NAME):

            log.info('Running full index build, as the changeset '

                     'index does not exist')

        else:

            self.initial = False

    def _get_index_revision(self, repo):

        landing_rev = 'tip'

        if db_repo:

            _rev_type, _rev = db_repo.landing_rev

            landing_rev = _rev

        return landing_rev

    def _get_index_changeset(self, repo, index_rev=None):

        if not index_rev:

            index_rev = self._get_index_revision(repo)

        cs = repo.get_changeset(index_rev)

        return cs

    def get_paths(self, repo):

        """

        recursive walk in root dir and return a set of all path in that dir

        based on repository walk function

        """

        index_paths_ = set()

        try:

            cs = self._get_index_changeset(repo)

            for _topnode, _dirs, files in cs.walk('/'):

                for f in files:

                    index_paths_.add(os.path.join(safe_str(repo.path), safe_str(f.path)))

        except RepositoryError:

            log.debug(traceback.format_exc())

            pass

        return index_paths_

    def get_node(self, repo, path, index_rev=None):

        """

        gets a filenode based on given full path. It operates on string for

        hg git compatibility.

        :param repo: scm repo instance

        :param path: full path including root location

        :return: FileNode

        """

        # FIXME: paths should be normalized ... or even better: don't include repo.path

        path = safe_str(path)

        repo_path = safe_str(repo.path)

        assert path.startswith(repo_path)

        assert path[len(repo_path)] in (os.path.sep, os.path.altsep)

        node_path = path[len(repo_path) + 1:]

        cs = self._get_index_changeset(repo, index_rev=index_rev)

        node = cs.get_node(node_path)

        return node

    scm = None

    DEFAULT_BRANCH_NAME = None

    EMPTY_CHANGESET = '0' * 40

    def __init__(self, repo_path, create=False, **kwargs):

        """

        Initializes repository. Raises RepositoryError if repository could

        not be find at the given ``repo_path`` or directory at ``repo_path``

        exists and ``create`` is set to True.

        :param repo_path: local path of the repository

        :param create=False: if set to True, would try to create repository.

        :param src_url=None: if set, should be proper url from which repository

          would be cloned; requires ``create`` parameter to be set to True -

          raises RepositoryError if src_url is set and create evaluates to

          False

        """

        raise NotImplementedError

    def __str__(self):

        return '<%s at %s>' % (self.__class__.__name__, self.path)

    def __repr__(self):

        return self.__str__()

    def __len__(self):

        return self.count()

    def __eq__(self, other):

        same_instance = isinstance(other, self.__class__)

        return same_instance and getattr(other, 'path', None) == self.path

    def __ne__(self, other):

        return not self.__eq__(other)

    @LazyProperty

    def alias(self):

        for k, v in settings.BACKENDS.items():

            if v.split('.')[-1] == str(self.__class__.__name__):

                return k

    @LazyProperty

    def name(self):

        """

        Return repository name (without group name)

        """

        raise NotImplementedError

    @LazyProperty

    def owner(self):

        raise NotImplementedError

    @LazyProperty

    def description(self):

        raise NotImplementedError

    @LazyProperty

    def size(self):

        """

        Returns combined size in bytes for all repository files

        """

        size = 0

        try:

            tip = self.get_changeset()

            for topnode, dirs, files in tip.walk('/'):

                for f in files:

                    size += tip.get_file_size(f.path)

        except RepositoryError as e:

            pass

        return size

    def is_valid(self):

        """

        Validates repository.

        """

        raise NotImplementedError

    def is_empty(self):

        return self._empty

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

    # CHANGESETS

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

    def get_changeset(self, revision=None):

        """

        Returns instance of ``Changeset`` class. If ``revision`` is None, most

        recent changeset is returned.

        :raises ``EmptyRepositoryError``: if there are no revisions

        """

        raise NotImplementedError

    def __iter__(self):