replace hard-coded /var/jenkins_home with $JENKINS_HOME
diff --git a/jenkins.sh b/jenkins.sh
index dd28123..1894c04 100755
--- a/jenkins.sh
+++ b/jenkins.sh
@@ -2,7 +2,7 @@
 
 set -e
 
-# Copy files from /usr/share/jenkins/ref into /var/jenkins_home
+# Copy files from /usr/share/jenkins/ref into $JENKINS_HOME
 # So the initial JENKINS-HOME is set with expected content.
 # Don't override, as this is just a reference setup, and use from UI
 # can then change this, upgrade plugins, etc.
@@ -13,15 +13,16 @@
 	rel="${b:23}"
 	dir=$(dirname "${b}")
 	echo " $f -> $rel" >> "$COPY_REFERENCE_FILE_LOG"
-	if [[ ! -e /var/jenkins_home/${rel} || $f = *.override ]]
+	if [[ ! -e $JENKINS_HOME/${rel} || $f = *.override ]]
 	then
 		echo "copy $rel to JENKINS_HOME" >> "$COPY_REFERENCE_FILE_LOG"
-		mkdir -p "/var/jenkins_home/${dir:23}"
-		cp -r "${f}" "/var/jenkins_home/${rel}";
+		mkdir -p "$JENKINS_HOME/${dir:23}"
+		cp -r "${f}" "$JENKINS_HOME/${rel}";
 		# pin plugins on initial copy
-		[[ ${rel} == plugins/*.jpi ]] && touch "/var/jenkins_home/${rel}.pinned"
+		[[ ${rel} == plugins/*.jpi ]] && touch "$JENKINS_HOME/${rel}.pinned"
 	fi;
 }
+: ${JENKINS_HOME:="/var/jenkins_home"}
 export -f copy_reference_file
 touch "${COPY_REFERENCE_FILE_LOG}" || (echo "Can not write to ${COPY_REFERENCE_FILE_LOG}. Wrong volume permissions?" && exit 1)
 echo "--- Copying files at $(date)" >> "$COPY_REFERENCE_FILE_LOG"