updated sage build

jupyter-sage/Dockerfile

@@ -1,4 +1,5 @@
 FROM debian:latest
+ARG VERSION
 RUN apt-get update && apt-get upgrade
 RUN apt-get install -y bc binutils bzip2 ca-certificates cliquer cmake curl \
         ecl eclib-tools fflas-ffpack g++ gap gcc gengetopt gfan gfortran \
@@ -30,7 +31,6 @@ RUN useradd jovyan -u 1000 -s /bin/bash -m -h /home/jovyan
 USER jovyan
 WORKDIR /home/jovyan
 COPY build.sh build.sh
-RUN git clone -c core.symlinks=true --filter blob:none  \
-    --origin upstream --branch master --tags \
-    https://github.com/sagemath/sage.git
+ADD --chown=luser:luser git@github.com:sagemath/sage.git#${VERSION} sage
+WORKDIR /home/jovyan/sage
 RUN export srcdir=/home/jovyan/sage source build.sh && prepare && build