When Louis C.K. flawlessly introduced the Best Documentary, Short Subject category at the Oscars, he said it’s his favorite because “this is the one Academy Award that has the opportunity to change a life.” He was talking about the filmmakers — “these people will not be rich as long as they live. All they do is tell stories that are important” — but in the case of the winner this year, it has the potential to change a great many lives. “A Girl in the River: The Price of Forgiveness,” premiering on HBO on March 7, tells the story of Saba, an attempted honor killing victim in Pakistan who survived.