Change to Dockerfile to improve layer caching. Includes temp hack due to implementation of setup.py

Author: Eric Smyth

Dockerfile

@@ -1,11 +1,13 @@
 FROM python:3.7.7-slim-buster
 RUN mkdir /app
 WORKDIR /app
-COPY .streamlit .streamlit
 COPY README.md .
 COPY setup.py .
+# Creating an empty src dir is a (hopefully) temporary hack to improve layer caching and speed up image builds
+# todo fix once the Pipfile, setup.py, requirements.txt, pyprojec.toml build/dist story is figured out
+RUN mkdir src && pip install -q .
+COPY .streamlit .streamlit
 COPY settings.cfg .
 COPY src src
-RUN pip install -q .
 
 CMD ["streamlit", "run", "src/app.py"]