How to use the dugite.GitError.PushNotFastForward function in dugite

const e = asErrorWithMetadata(error)
  if (!e) {
    return error
  }

  const gitError = asGitError(e.underlyingError)
  if (!gitError) {
    return error
  }

  const dugiteError = gitError.result.gitError
  if (!dugiteError) {
    return error
  }

  if (dugiteError !== DugiteError.PushNotFastForward) {
    return error
  }

  const repository = e.metadata.repository
  if (!repository) {
    return error
  }

  if (!(repository instanceof Repository)) {
    return error
  }

  // Since they need to pull, go ahead and do a fetch for them.
  dispatcher.fetch(repository, FetchType.UserInitiatedTask)

  return error

case DugiteError.HTTPSAuthenticationFailed:
      return `Authentication failed. You may not have permission to access the repository or the repository may have been archived. Open ${
        __DARWIN__ ? 'preferences' : 'options'
      } and verify that you're signed in with an account that has permission to access this repository.`
    case DugiteError.RemoteDisconnection:
      return 'The remote disconnected. Check your Internet connection and try again.'
    case DugiteError.HostDown:
      return 'The host is down. Check your Internet connection and try again.'
    case DugiteError.RebaseConflicts:
      return 'We found some conflicts while trying to rebase. Please resolve the conflicts before continuing.'
    case DugiteError.MergeConflicts:
      return 'We found some conflicts while trying to merge. Please resolve the conflicts and commit the changes.'
    case DugiteError.HTTPSRepositoryNotFound:
    case DugiteError.SSHRepositoryNotFound:
      return 'The repository does not seem to exist anymore. You may not have access, or it may have been deleted or renamed.'
    case DugiteError.PushNotFastForward:
      return 'The repository has been updated since you last pulled. Try pulling before pushing.'
    case DugiteError.BranchDeletionFailed:
      return 'Could not delete the branch. It was probably already deleted.'
    case DugiteError.DefaultBranchDeletionFailed:
      return `The branch is the repository's default branch and cannot be deleted.`
    case DugiteError.RevertConflicts:
      return 'To finish reverting, please merge and commit the changes.'
    case DugiteError.EmptyRebasePatch:
      return 'There aren’t any changes left to apply.'
    case DugiteError.NoMatchingRemoteBranch:
      return 'There aren’t any remote branches that match the current branch.'
    case DugiteError.NothingToCommit:
      return 'There are no changes to commit.'
    case DugiteError.NoSubmoduleMapping:
      return 'A submodule was removed from .gitmodules, but the folder still exists in the repository. Delete the folder, commit the change, then try again.'
    case DugiteError.SubmoduleRepositoryDoesNotExist: