SAN FRANCISCO — Mike Foltynewicz made one mistake on the mound and it cost him the ballgame. That home run pitch to Buster Posey bothered him, but his inability to get a bunt down bothered him more. Posey hit a two-run homer in the first inning and drove in three, and though Foltynewicz nearly matched Tim Hudson with 6 2/3 strong innings, the Atlanta Braves lost 4-2 to the surging San Francisco Giants on Friday night.