Add a simple build script to build docker images and a basic dockerfile

build

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+#!/bin/bash
+
+set -eu
+
+# Builds the docker images.
+# Usage: ./build {COMPONENTS}, or just ./build to build all.
+# The resulting images are named wubloader-COMPONENT.
+
+# The different images we can build
+COMPONENTS=(downloader)
+
+# The docker image tag, derived from the git commit + whether working tree is clean
+TAG=$(git rev-parse --short HEAD)
+if [ -n "$(git status --porcelain --untracked-files=no)" ]; then
+	TAG="$TAG-wip"
+fi
+
+if [ "$#" -gt 0 ]; then
+	COMPONENTS=("$@")
+fi
+
+for component in "${COMPONENTS[@]}"; do
+	echo "Building image for $component"
+	docker build \
+		-f "$component/Dockerfile" \
+		-t "wubloader-$component:latest" \
+		-t "wubloader-$component:$TAG" \
+		.
+	echo "Built image wubloader-$component:$TAG"
+done

downloader/Dockerfile

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+FROM alpine:3.7
+RUN apk --update add py2-pip
+
+# Install common lib first as it changes less
+COPY common /tmp/common
+RUN pip install /tmp/common && rm -r /tmp/common
+
+# Install actual application
+COPY downloader /tmp/downloader
+RUN pip install /tmp/downloader && rm -r /tmp/downloader
+
+# Add config file last as it changes most
+COPY config.yaml /etc/wubloader.yaml
+
+CMD python2 -m downloader