Before it was a Tony Award-winning Broadway musical, “Once” was a scruffy and charming movie, written and directed by John Carney, about a man and a woman united by their love of music and their unstated but obvious attraction to each other. Filmed at street level in the lived-in parts of a picturesque city, it managed to be touristic and authentic at the same time, partly because the central pair consisted of a native and an outsider. Mr. Carney pulled off the enviable trick of dressing unabashed romantic sentiment in a style that felt rough and real, so that every cliché he touched felt shiny and new.