Beginning today, Sundance is devoting part of its schedule to a truly welcome TV retrospective: in-sequence giant helpings of some of the best TV comedies ever made. Sunday from 6 a.m. ET through Tuesday at the same time, Sundance works its way through a marathon showing of the first four seasons of M*A*S*H, the brilliant anti-war war comedy developed for television by Larry Gelbert in 1972. That’s followed, on Tuesday, by heaping helpings of another 1970s TV classic, All in the Family. Collect them all. Trade with friends. And this, I hope, is just a taste of things to come. What TV needs next is an entire programming block, if not network, that takes TV as seriously as TCM treats film: with documentary specials, focused retrospectives, insider guests, and other treats. But for starters, let’s salute Sundance for what it’s doing here.