Combine COPY directives to elide a layer

Dockerfile

@@ -2,8 +2,10 @@ FROM anapsix/alpine-java:jre7
 MAINTAINER Andrew Gaul <andrew@gaul.org>
 
 WORKDIR /opt/s3proxy
-COPY target/s3proxy /opt/s3proxy/
-COPY src/main/resources/run-docker-container.sh /opt/s3proxy/
+COPY \
+    target/s3proxy \
+    src/main/resources/run-docker-container.sh \
+    /opt/s3proxy/
 
 ENV \
     LOG_LEVEL="info" \