def _insert_common_sphinx_configs(c, *, project_name):
    """Add common core Sphinx configurations to the state.
    """
    c['project'] = project_name
    c['source_suffix'] = '.rst'
    c['source_encoding'] = 'utf-8-sig'
    c['master_doc'] = 'index'
    c['numfig'] = True
    c['numfig_format'] = {'figure': 'Figure %s', 'table': 'Table %s',
        'code-block': 'Listing %s'}
    c['default_role'] = 'obj'
    c['rst_epilog'] = '\n.. _Astropy: http://astropy.org\n    '
    c['suppress_warnings'] = ['app.add_directive']
    return c
