An Emacs config I use to make SLY's tramp contrib work with Ultralisp docker containers.

ultralisp.local.el

(require 'sly)

(defun sly-ultralisp-init ()
  (defun sly-make-tramp-file-name (username remote-host lisp-filename)
    "Old (with multi-hops) tramp compatability function"
    (message "Makining tramp filename for %s %s and %s" username remote-host lisp-filename)
    (tramp-make-tramp-file-name "docker"
                                username
                                nil
                                remote-host
                                nil
                                lisp-filename))

  (defun sly-docker-on-connection ()
    (add-to-list 'sly-filename-translations
                 (sly-create-filename-translator
                  :machine-instance "ultralisp_app"
                  :username "root"))


    (add-to-list 'sly-filename-translations
                 (sly-create-filename-translator
                  :machine-instance "ultralisp_worker"
                  :username "root"))

    (let* ((host (sly-machine-instance))
           (docker-output (shell-command-to-string "docker ps --format '{{.ID}} {{.Names}}'"))
           (containers (split-string docker-output))
           (pos (position host containers :test 'string=)))
      (when pos
        ;; If we found a real container's name, then we'll
        ;; replace sly-machine-instance to it to have
        ;; nice hosts for tramp.
        (let ((container-name (nth (1+ pos) containers)))
          (setf (sly-machine-instance)
                container-name)))))
  
  (add-hook 'sly-connected-hook 'sly-docker-on-connection))


(add-hook 'sly-mode-hook
          'sly-ultralisp-init)