Merge branch 'tag-exists' into 'master'
Use tag_exists? in GitAccess#protected_tag? This will fail until https://gitlab.com/gitlab-org/gitlab_git/merge_requests/81/ is merged. Adding this should speed up checking for tags in `Gitlab::GitAccess` as it no longer needs to retrieve the entire list of tags. See https://gitlab.com/gitlab-org/gitlab-ce/issues/14280 for more information. See merge request !3983