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

    @property

    def name_unicode(self):

        return safe_unicode(self.name)

    @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):

        """

        Allows Repository objects to be iterated.

        *Requires* implementation of ``__getitem__`` method.

        """

        for revision in self.revisions:

            yield self.get_changeset(revision)

    def get_changesets(self, start=None, end=None, start_date=None,

                       end_date=None, branch_name=None, reverse=False):

        """

        :param start: None or str

        :param end: None or str

        :param start_date:

        :param end_date:

        :param branch_name:

        :param reversed:

        """

        raise NotImplementedError

    def __getslice__(self, i, j):

        """

        Returns a iterator of sliced repository

        """

        for rev in self.revisions[i:j]:

            yield self.get_changeset(rev)

    def __getitem__(self, key):

        return self.get_changeset(key)

    def count(self):

        return len(self.revisions)

    def tag(self, name, user, revision=None, message=None, date=None, **opts):

        """

        Creates and returns a tag for the given ``revision``.

        :param name: name for new tag

        :param user: full username, i.e.: "Joe Doe <joe.doe@example.com>"

        :param revision: changeset id for which new tag would be created

        :param message: message of the tag's commit

        :param date: date of tag's commit

        :raises TagAlreadyExistError: if tag with same name already exists

        """

        raise NotImplementedError

    def remove_tag(self, name, user, message=None, date=None):

        """

        Removes tag with the given ``name``.

        :param name: name of the tag to be removed

        :param user: full username, i.e.: "Joe Doe <joe.doe@example.com>"

        :param message: message of the tag's removal commit

        :param date: date of tag's removal commit

        :raises TagDoesNotExistError: if tag with given name does not exists

        """

        raise NotImplementedError

    def get_diff(self, rev1, rev2, path=None, ignore_whitespace=False,

            context=3):

        """

        Returns (git like) *diff*, as plain text. Shows changes introduced by

        ``rev2`` since ``rev1``.

        :param rev1: Entry point from which diff is shown. Can be

          ``self.EMPTY_CHANGESET`` - in this case, patch showing all

          the changes since empty state of the repository until ``rev2``

        :param rev2: Until which revision changes should be shown.

        :param ignore_whitespace: If set to ``True``, would not show whitespace

          changes. Defaults to ``False``.

        :param context: How many lines before/after changed lines should be

          shown. Defaults to ``3``.

        """

        raise NotImplementedError

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

    # COMMIT API #

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

    @LazyProperty

    def in_memory_changeset(self):

        """

        Returns ``InMemoryChangeset`` object for this repository.

        """

        raise NotImplementedError

    def add(self, filenode, **kwargs):

        """

        Commit api function that will add given ``FileNode`` into this

        repository.

        :raises ``NodeAlreadyExistsError``: if there is a file with same path

          already in repository

        :raises ``NodeAlreadyAddedError``: if given node is already marked as

          *added*

        """

        raise NotImplementedError

    def remove(self, filenode, **kwargs):

        """

        Commit api function that will remove given ``FileNode`` into this

        repository.

        :raises ``EmptyRepositoryError``: if there are no changesets yet