Oliver Stone, who eschewed politics for the TV-movie-ish “World Trade Center,” will revisit the Vietnam war for the fourth time with “Pinkville.” Bruce Willis will be back in uniform as an Army general investigating the My Lai massacre, and rising star Channing Tatum (“A Guide to Recognizing Your Saints”) will play a helicopter pilot who tried to stop the attack on unarmed civilians and reported it to authorities. The film is being produced by United Artists, co-headed by Tom Cruise, who starred in one of Stone’s earlier Vietnam-themed flicks, “Born on the Fourth of July.” The others are “Heaven and Earth” and, of course, the Oscar-winning “Platoon.”