Got this working with a basic sync of just the curatend/app directory…

… into the /app/app directory in the container.

docker-compose.yml

@@ -24,14 +24,13 @@ services:
       context: .
       dockerfile: docker/Dockerfile.rails
     command: bundle exec thin start -p 3000 --ssl --ssl-key-file dev_server_keys/server.key --ssl-cert-file dev_server_keys/server.crt
-    environment:
-      BUNDLE_PATH: "/bundle"
-      BUNDLE_DISABLE_SHARED_GEMS: "true"
-      BUNDLE_WITHOUT: "headless"
-    volumes:
-      - .:/myapp
     ports:
       - "3000:3000"
+    volumes:
+      - rails-app-sync:/app/app:nocopy
     depends_on:
       - mysql
       - jetty
+volumes:
+  rails-app-sync:
+    external: true

docker-sync.yml

@@ -0,0 +1,9 @@
+version: "2"
+
+options:
+  verbose: true
+syncs:
+  rails-app-sync: # tip: add -sync and you keep consistent names as a convention
+    src: './app'
+    # sync_strategy: 'native_osx' # not needed, this is the default now
+    sync_excludes: ['ignored_folder', '.ignored_dot_folder']

docker/Dockerfile.rails

@@ -2,12 +2,8 @@ FROM ruby:2.1.10
 
 RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
 RUN mkdir /app
-RUN mkdir /bundle
-
-WORKDIR /bundle
-COPY Gemfile /bundle/Gemfile
-COPY Gemfile.lock /bundle/Gemfile.lock
-RUN bundle install  --without headless --path /bundle
 
 WORKDIR /app
 COPY . /app
+
+RUN bundle install  --without headless