Port: a minimalist prepl client for Emacs

For ages I’ve had “add prepl support to CIDER” sitting somewhere in the back of my head. CIDER is built firmly around nREPL, but prepl ships with Clojure itself, and the appeal of dropping the external REPL server requirement is obvious. Recently, as part of a broader internals cleanup “mini-project” in CIDER, I finally sat down and put a prototype together: cider#3899.The good news is that the prototype sort of worked. The bad news is that the more I poked at it, the more I kept running into the same pattern. CIDER assumes ops, sessions, request ids, and a whole structured protocol that prepl simply doesn’t have. The amount of CIDER code that would need to grow “is this nREPL or prepl?” branches added up quickly, and I’d be papering over prepl’s limitations in dozens of subtle places. The exercise was fun, but it ended up reaffirming my long-standing belief that nREPL is a much better fit for editor tooling than prepl is.The exercise did leave me thinking though. What if, instead of…