Draft: specifying default connection params

[yuhan0]

Context: https://clojurians.slack.com/archives/C0617A8PQ/p1687640686417379

As discussed on Slack, a naive clj-only implementation of a feature which allows the user to skip cider-connect prompts asking for the hostname and port.

The intended usage here is to set cider-default-connect-params explicitly per project as a dir-local variable, which is why it's a defvar-local instead of defcustom.

Eg. I have a project which specifies in its deps.edn

{:aliases {:dev 
   :main-opts ["-m" "nrepl.cmdline" "--port" "2171" ,,,],,,},,,} 

so running clj -M:dev in an external terminal always starts a Cider nrepl server on the port 2171.

Then in the project's .dir-locals.el:

((clojure-mode
  . ((cider-connect-default-params . (:host "localhost" :port 2171)))))

Result: M-x cider-connect on any clj buffer within that project skips the prompts entirely, saving the friction of a couple of RET RET keypresses on every connect. Which can be quite frequent when investigating project crashes (or hacking on Cider itself)

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