except Exception:

                log.error(traceback.format_exc())

                raise

        try:

            f = UserFollowing()

            f.user_id = user_id

            f.follows_user_id = follow_user_id

            Session().add(f)

        except Exception:

            log.error(traceback.format_exc())

            raise

    def is_following_repo(self, repo_name, user_id, cache=False):

        r = Repository.query() \

            .filter(Repository.repo_name == repo_name).scalar()

        f = UserFollowing.query() \

            .filter(UserFollowing.follows_repository == r) \

            .filter(UserFollowing.user_id == user_id).scalar()

        return f is not None

    def is_following_user(self, username, user_id, cache=False):

        u = User.get_by_username(username)

        f = UserFollowing.query() \

            .filter(UserFollowing.follows_user == u) \

            .filter(UserFollowing.user_id == user_id).scalar()

        return f is not None

    def get_followers(self, repo):

        repo = Repository.guess_instance(repo)

        return UserFollowing.query() \

                .filter(UserFollowing.follows_repository == repo).count()

    def get_forks(self, repo):

        repo = Repository.guess_instance(repo)

        return Repository.query() \

                .filter(Repository.fork == repo).count()

    def get_pull_requests(self, repo):

        repo = Repository.guess_instance(repo)

        return PullRequest.query() \

                .filter(PullRequest.other_repo == repo) \

                .filter(PullRequest.status != PullRequest.STATUS_CLOSED).count()

    def mark_as_fork(self, repo, fork, user):

        repo = self.__get_repo(repo)

        fork = self.__get_repo(fork)

        if fork and repo.repo_id == fork.repo_id:

            raise Exception("Cannot set repository as fork of itself")

        if fork and repo.repo_type != fork.repo_type:

            raise RepositoryError("Cannot set repository as fork of repository with other type")

        repo.fork = fork

        return repo

    def _handle_rc_scm_extras(self, username, repo_name, repo_alias,

                              action=None):

        from kallithea import CONFIG

        from kallithea.lib.base import _get_ip_addr

        try:

            from tg import request

            environ = request.environ

        except TypeError:

            # we might use this outside of request context, let's fake the

            # environ data

            from webob import Request

            environ = Request.blank('').environ

        extras = {

            'ip': _get_ip_addr(environ),

            'username': username,

            'action': action or 'push_local',

            'repository': repo_name,

            'scm': repo_alias,

            'config': CONFIG['__file__'],

            'server_url': get_server_url(environ),

            'make_lock': None,

            'locked_by': [None, None]

        }

        _set_extras(extras)

    def _handle_push(self, repo, username, action, repo_name, revisions):

        """

        Triggers push action hooks

        :param repo: SCM repo

        :param username: username who pushes

        :param action: push/push_local/push_remote

        :param repo_name: name of repo

        :param revisions: list of revisions that we pushed

        """

        _scm_repo = repo._repo

        # trigger push hook

        if repo.alias == 'hg':

            log_push_action(_scm_repo.ui, _scm_repo, node=revisions[0])

        elif repo.alias == 'git':

            log_push_action(None, _scm_repo, _git_revs=revisions)

    def _get_IMC_module(self, scm_type):

        """

        Returns InMemoryCommit class based on scm_type

        :param scm_type:

        """

        if scm_type == 'hg':

            from kallithea.lib.vcs.backends.hg import MercurialInMemoryChangeset

            return MercurialInMemoryChangeset

        if scm_type == 'git':

            from kallithea.lib.vcs.backends.git import GitInMemoryChangeset

            return GitInMemoryChangeset

        raise Exception('Invalid scm_type, must be one of hg,git got %s'

                        % (scm_type,))

    def pull_changes(self, repo, username, clone_uri=None):

        """

        Pull from "clone URL" or fork origin.

        """

        dbrepo = self.__get_repo(repo)

        if clone_uri is None:

            clone_uri = dbrepo.clone_uri or dbrepo.fork and dbrepo.fork.repo_full_path

        if not clone_uri:

            raise Exception("This repository doesn't have a clone uri")

        repo = dbrepo.scm_instance

        repo_name = dbrepo.repo_name

        try:

            if repo.alias == 'git':

                repo.fetch(clone_uri)

                # git doesn't really have something like post-fetch action

                # we fake that now. #TODO: extract fetched revisions somehow

                # here

                self._handle_push(repo,

                                  username=username,

                                  action='push_remote',

                                  repo_name=repo_name,

                                  revisions=[])

            else:

                self._handle_rc_scm_extras(username, dbrepo.repo_name,

                                           repo.alias, action='push_remote')

                repo.pull(clone_uri)

            self.mark_for_invalidation(repo_name)

        except Exception:

            log.error(traceback.format_exc())

            raise

    def commit_change(self, repo, repo_name, cs, user, author, message,

                      content, f_path):

        """

        Commit a change to a single file

        :param repo: a db_repo.scm_instance

        """

        user = User.guess_instance(user)

        IMC = self._get_IMC_module(repo.alias)

        # decoding here will force that we have proper encoded values

        # in any other case this will throw exceptions and deny commit

        content = safe_str(content)

        path = safe_str(f_path)

        # message and author needs to be unicode

        # proper backend should then translate that into required type

        message = safe_unicode(message)

        author = safe_unicode(author)

        imc = IMC(repo)

        imc.change(FileNode(path, content, mode=cs.get_file_mode(f_path)))

        try:

            tip = imc.commit(message=message, author=author,

                             parents=[cs], branch=cs.branch)

        except Exception as e:

            log.error(traceback.format_exc())

            raise IMCCommitError(str(e))

        finally:

            # always clear caches, if commit fails we want fresh object also

            self.mark_for_invalidation(repo_name)

        self._handle_push(repo,

                          username=user.username,

                          action='push_local',

                          repo_name=repo_name,

                          revisions=[tip.raw_id])

        return tip

    def _sanitize_path(self, f_path):

        if f_path.startswith('/') or f_path.startswith('.') or '../' in f_path:

            raise NonRelativePathError('%s is not an relative path' % f_path)