fix(docker): properly propagate default ARG PORT

Shell parameter expansion doesn't happen inside the CMD array, one either needs to pass an ENV var and use it in an entrypoint shell script or, if one doesn't want to pollute the container's env space, modify the argument (with sed) within the entrypoint itself.

Also ignore a couple fat directories that complicate local development.

.dockerignore

@@ -7,3 +7,5 @@
 .pytest_cache
 .mypy_cache
 /.idea
+.tox
+.make-cache

Dockerfile

@@ -49,18 +49,21 @@ RUN chown $USER_NAME $STORAGE_DIR
 ARG EXTRA_PACKAGES="wsgi_cors_middleware"
 RUN pip install ${EXTRA_PACKAGES}
 
-USER $USER_NAME
-
 WORKDIR /app
 
 ENV UWSGI_MODULE "giftless.wsgi_entrypoint"
 
 ARG PORT=5000
 EXPOSE $PORT
+# embed the default port into docker-entrypoint.sh, and make it executable
+RUN set -eu ;\
+    de=scripts/docker-entrypoint.sh ;\
+    sed -i "/^default_port=/s/5000/$PORT/" "$de" ;\
+    chmod +x "$de"
+
+USER $USER_NAME
+
+ENTRYPOINT ["tini", "--", "scripts/docker-entrypoint.sh"]
 
-ENTRYPOINT ["tini", "uwsgi", "--"]
 # TODO remove this STOPSIGNAL override after uwsgi>=2.1
 STOPSIGNAL SIGQUIT
-
-CMD ["-s", "127.0.0.1:${PORT}", "-M", "-T", "--threads", "2", "-p", "2", \
-     "--manage-script-name", "--callable", "app"]

scripts/docker-entrypoint.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+default_port=5000
+if [ $# -eq 0 ]; then
+  # listen on localhost:PORT by default
+  exec uwsgi -s "127.0.0.1:$default_port" -M -T --threads 2 -p 2 --manage-script-name --callable app
+else
+  # use custom arguments
+  exec uwsgi "$@"
+fi