[docker] build the git-bridge in docker

Signed-off-by: Jakob Ackermann <das7pad@outlook.com>

services/git-bridge/Dockerfile

@@ -13,4 +13,21 @@ RUN apt-get update && \
 
 
 RUN mkdir /app
-WORKDIR /app
+WORKDIR /app
+
+COPY . /app
+RUN mvn clean package \
+# The name of the created jar contains the current version tag.
+# Rename it to a static path that can be used for copying.
+&&  find /app/target \
+      -name 'writelatex-git-bridge*jar-with-dependencies.jar' \
+      -exec mv {} /git-bridge.jar \;
+
+FROM openjdk:8-jre
+
+USER www-data
+
+ENTRYPOINT ["java", "-jar", "/git-bridge.jar"]
+CMD ["/conf/runtime.json"]
+
+COPY --from=0 /git-bridge.jar /