Dockerfile in r10k-3.3.1

- old
+ new

@@ -1,5 +1,14 @@
+FROM alpine:3.9 as build
+
+RUN apk add --no-cache ruby git
+RUN mkdir /workspace
+WORKDIR /workspace
+COPY . /workspace
+RUN gem build r10k.gemspec && \
+    mv r10k*.gem r10k.gem
+
 FROM alpine:3.9
 
 ARG vcs_ref
 ARG build_date
 ARG version="3.1.0"
@@ -21,16 +30,17 @@
       org.label-schema.build-date="$build_date" \
       org.label-schema.schema-version="1.0" \
       org.label-schema.dockerfile="/Dockerfile"
 
 RUN apk add --no-cache ruby openssh-client git ruby-rugged curl ruby-dev make gcc musl-dev
+COPY --from=build /workspace/r10k.gem /
+RUN gem install --no-doc r10k.gem json etc && \
+    rm -f r10k.gem
 
-RUN gem install --no-doc r10k:"$R10K_VERSION" json etc
-
-COPY docker-entrypoint.sh /
+COPY docker/r10k/docker-entrypoint.sh /
 RUN chmod +x /docker-entrypoint.sh
-COPY docker-entrypoint.d /docker-entrypoint.d
+COPY docker/r10k/docker-entrypoint.d /docker-entrypoint.d
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 CMD ["help"]
 
-COPY Dockerfile /
+COPY docker/r10k/Dockerfile /