SAN FRANCISCO — Casey Schmitt did it again. The day after giving the Giants the lead with a late blast to left field, Schmitt showed off his clutch gene to the Marlins’ bullpen for a second time in as many games . Schmitt launched a three-run shot to left in the seventh inning that broke a tie and gave the Giants their first lead in an eventual 6-3 win to secure the three-game series. Giants pitcher Landen Roupp had the longest start of his career Sunday in a victory over the Marlins. IMAGN IMAGES via Reuters Connect The heroics ensured the longest start of Landen Roupp’s career didn’t go to waste. Roupp took the mound to start the eighth inning for the first time in his career and was serenaded by a standing ovation as he walked back to the dugout with two outs. The bases on balls that ended his outing was only the fourth Marlins batter to reach base against him and snapped a streak of 18 retired in a row.…