Single map arg for easier programmatic interop

[borkdude]

In babashka I'm embedding deps.clj and it looks as follows:

(binding [deps/*aux-process-fn*
          (fn [{:keys [cmd out]}]
            (apply process/shell {:out out
                                  :env env
                                  :dir (when deps-root (str deps-root))
                                  :extra-env extra-env} cmd))])

It would be nicer if we could just pass the cmd as well.

When cmd is provided, any additional arguments are ignored.