Added JUGGLER_DETECTOR_VERSION to clone specific branch

- This can be a tag or a branch (uses `git clone -b X`)

options/env.sh

@@ -34,6 +34,11 @@ if [ ! -n  "${JUGGLER_DETECTOR}" ] ; then
 fi
 echo "JUGGLER_DETECTOR:       ${JUGGLER_DETECTOR}"
 
+if [ ! -n  "${JUGGLER_DETECTOR_VERSION}" ] ; then 
+  export JUGGLER_DETECTOR_VERSION="v0.0.1"
+fi
+echo "JUGGLER_DETECTOR_VERSION:       ${JUGGLER_DETECTOR_VERSION}"
+
 ## Number of events that will be processed by the reconstruction
 if [ ! -n  "${JUGGLER_N_EVENTS}" ] ; then 
   export JUGGLER_N_EVENTS=100

util/build_detector.sh

@@ -29,7 +29,7 @@ pushd ${DETECTOR_PREFIX}
 ## We need an up-to-date copy of the detector
 if [ ! -d ${JUGGLER_DETECTOR} ]; then
   echo "Fetching ${JUGGLER_DETECTOR}"
-  git clone https://eicweb.phy.anl.gov/EIC/detectors/${JUGGLER_DETECTOR}.git
+  git clone -b ${JUGGLER_DETECTOR_VERSION} https://eicweb.phy.anl.gov/EIC/detectors/${JUGGLER_DETECTOR}.git
 else
   echo "Updating ${JUGGLER_DETECTOR}"
   pushd ${JUGGLER_DETECTOR}