It is movie time again in East Hampton. Next Thursday at Guild Hall, the Hamptons International Film Festival officially opens with the screening of “Just Mercy.” From then until the afternoon of Oct. 14, it will be a cinephile’s delight, with dozens of features and short films, as well as talks and parties, from all over the world and homegrown directors, writers, and producers, famous and not so famous. With this much to choose from in a short few days, just choosing what to see can seem daunting. Tickets have gone on sale, and while some of the biggest titles might be sold out, there are always plenty of other choices.