To constitute an ordinance of the city council it must, before final action thereon, be advertised once at least two days before its adoption, and in case of any amendment being made thereto, before the final adoption of the ordinance, such ordinance as amended must in like manner be advertised once at least three days before final adoption. The advertisement of an ordinance shall be by publication in at least one edition of the official newspaper of the city, except that upon (1) unanimous vote of the councilmembers present at the meeting when such ordinance is introduced or amendment proposed, the advertisement may be done by posting a copy of such original ordinance or amended ordinance on the bulletin board at the City Hall and, (2) at the direction of the city council, a synopsis of the ordinance may be published in lieu of the ordinance in its entirety and the entire text of the ordinance shall be available to the public through the office of the city clerk.