SAN FRANCISCO — Jared Oliva is 30 years old and hasn’t played in the big leagues since 2021, when he struggled in 40 at-bats for the Pittsburgh Pirates. He spent all of last season in Triple-A with the Milwaukee Brewers and the previous year in Double-A with the Seattle Mariners, and his recent history includes time in the Mexican Winter League. Oliva admitted Wednesday that there were times when it probably made sense to give up on this whole baseball dream. “It felt like I was going against the current,” he said, smiling. For the time being, at least, the only body of water Oliva has to worry about is the one behind his new ballpark. The Giants selected him to their roster on Wednesday morning, choosing him over 24-year-old Luis Matos, a former top prospect, and a couple of left-handed options. Manager Tony Vitello lit up when talking about giving Oliva the news. President of baseball operations Buster Posey said it was a roster move that thrilled everyone “to a man” in the coaches’ room and clubhouse.“With a lot of hard conversations the last few days, that one was one that stood out as a real bright spot to...