Enable building COmanage Registry from file in build context

Add logic so that if a gzipped tarball with the COmanage Registry
source code is in the build context it can be referenced using
the build argument COMANAGE_REGISTRY_BUILD_SRC, for example
COMANAGE_REGISTRY_BUILD_SRC=file:///tmp/build/comanage.tar.gz
This allows building an image using a local copy of the source
instead of downloading from GitHub.

comanage-registry-base/Dockerfile

@@ -57,10 +57,14 @@ ARG COMANAGE_REGISTRY_DIR
 ENV COMANAGE_REGISTRY_DIR ${COMANAGE_REGISTRY_DIR:-/srv/comanage-registry}
 LABEL comanage_registry_dir=${COMANAGE_REGISTRY_DIR}
 
+RUN mkdir -p /tmp/build
+COPY . /tmp/build
+
 WORKDIR $COMANAGE_REGISTRY_DIR
 
 RUN mkdir -p ${COMANAGE_REGISTRY_DIR} \
-      && wget -O comanage.tar.gz ${COMANAGE_REGISTRY_SRC_URL} \
+      && echo "Using COMANAGE_REGISTRY_SRC_URL ${COMANAGE_REGISTRY_SRC_URL}" \
+      && curl -L -o comanage.tar.gz ${COMANAGE_REGISTRY_SRC_URL} \
       && tar -zxf comanage.tar.gz -C ${COMANAGE_REGISTRY_DIR} --strip-components=1 \
       && rm -f comanage.tar.gz \
       && rm -f ${COMANAGE_REGISTRY_DIR}/app/tmp \
@@ -70,6 +74,8 @@ RUN mkdir -p ${COMANAGE_REGISTRY_DIR} \
       && ln -s ${COMANAGE_REGISTRY_DIR}/app/webroot registry \
       && rm -rf ${COMANAGE_REGISTRY_DIR}/local/*
 
+RUN rm -rf /tmp/build
+
 ARG CACHEDIR
 ENV CACHEDIR ${CACHEDIR:-/srv/comanage-registry/app/tmp/cache}