message: add some comments describing the process.
diff: @@ -10,13 +10,23 @@ for datadir in $(ls -d /var/solr/*) ; do
  corename=$(basename $datadir)
  if [ -d ${datadir}/data ]; then
  echo "${datadir}/data is in old format, moving to ${datadir}."
  + # the contents of data have been moved to {datadir}/
  + # the datadir now has the layout that a newly created core would.
  mv ${datadir}/data/* ${datadir}/
  + # remove empty directory
  rm -Rf ${datadir}/data
  fi
  + # the new place for config is in the container, in /opt/solr/server/solr/${corename}
  mkdir -p /opt/solr/server/solr/${corename}
  +
  + # construct a core from the persistent volume into the container;
  + # there must be a core.properties to be recognized as a core
  + # this need not be done when the entire config is properly built into the image.
  cp -R ${datadir}/conf /opt/solr/server/solr/${corename}/
  touch /opt/solr/server/solr/${corename}/core.properties
  +
  + # update datadir to point to the persistent volume.
  sed -ibak 's/<dataDir>.*/<dataDir>\/var\/solr\/${solr.core.name}<\/dataDir>/' /opt/solr/server/solr/${corename}/conf/solrconfig.xml
  done
  