An Ashkenazi Jew walks into a Neo-Nazi meeting … . That may sound like a wind-up for a kitschy Borscht Belt punchline but it’s what comedian Alex Edelman actually did one fateful night in Queens. Hilarity and terror ensued, in equal measure. A nerdy standup comic who can’t help wanting everyone to like him, Edelman regales us with a wonderfully wry and wisecracking tale of jigsaw puzzles, Jewish identity and, yes, jiving his way into a white nationalist club in his euphorically funny solo show “Just for Us,” now at Berkeley Repertory Theatre through Jan. 21 after a Broadway run....