Minimal multi-stage docker build

Dockerfile

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+# ---- Base ----
+FROM python:alpine AS base
+
+#
+# ---- Dependencies ----
+FROM base AS dependencies
+# install dependencies
+COPY requirements.txt .
+RUN pip install -r requirements.txt
+ 
+#
+# ---- Release ----
+FROM dependencies AS release
+# copy project file(s)
+WORKDIR /
+COPY cloudflare-ddns.py .
+COPY config.json .
+CMD ["python", "/cloudflare-ddns.py"]