Mac Williamson homered in the fifth inning and hit a tiebreaking single in the 12th, lifting San Francisco over the New York Yankees 2-1 Saturday for the Giants' first victory since the All-Star break. NL West-leading San Francisco had lost a season-high six straight games and had held just one lead since the break: when Buster Posey hit a go-ahead home run leading off the 10th inning at San Diego on July 16 only to have the Padres rally for a pair of runs in the bottom half against Santiago Casilla. Williamson, whose fourth-inning error allowed the Yankees' run, began the comeback when he connected off Ivan Nova leading off the fifth.