It’s a few minutes before the house lights come down at the Brooklyn Academy of Music for the premiere of Spike Lee’s new “joint,” Da Republic of Brooklyn. Standing off to the side—largely unnoticed—is Lee himself. He gives the occasional thumbs-up to the few who recognize him in his ordinary getup: black track pants, a white Nike windbreaker and a baseball cap. When he takes the stage, Lee keeps his comments to under a minute: It’s good to be “in the Fort” he tells the packed house, a reference to the Fort Greene neighborhood where Lee keeps a studio. “Thank you for coming out.” And that’s pretty much it. Lee makes his exit.