Clone the default branch for Bitbucket importers
As seen in https://gitlab.com/gitlab-org/gitlab-ce/issues/59347, we likely will have to set the default branch properly for Bitbucket Server and Cloud importers.
As seen in https://gitlab.com/gitlab-org/gitlab-ce/issues/59347, we likely will have to set the default branch properly for Bitbucket Server and Cloud importers.