Gita consists of all scriptures (viz. the vital essence of all scriptures is embedded within Gita). God Sri Hari is in the form of all gods. Ganga holds within her all holy places and Manu (His Manusmriti) holds within it, all Vedas.
सर्वशास्त्रमयी गीता सर्वदेवमयो हरिः। सर्वतीर्थमयी गङ्गा सर्ववेदमयो मनुः॥