def update_default_branch(repositoryName=None, defaultBranchName=None):
    """
    Sets or changes the default branch name for the specified repository.
    See also: AWS API Documentation
    
    
    :example: response = client.update_default_branch(
        repositoryName='string',
        defaultBranchName='string'
    )
    
    
    :type repositoryName: string
    :param repositoryName: [REQUIRED]
            The name of the repository to set or change the default branch for.
            

    :type defaultBranchName: string
    :param defaultBranchName: [REQUIRED]
            The name of the branch to set as the default.
            

    """
    pass
