Use Dockerfile variable instead [complete]

README.md

@@ -26,7 +26,6 @@ docker run -i --privileged \
 -e DRUSH_DATABASE='ds990108' \
 -e DRUSH_EGROUP='drupal-admins-test-edu-d8-ldap' \
 -e DRUSH_OWNER='eduardoa' \
--e DRUSH_DRUPAL_VERSION='8.5.6' \
 -t <image_id> /bin/bash
 ```
 or with a file

drush/drushrc.php

 <?php
 $options['uri'] = '$DRUSH_SITENAME';
-$options['root'] = '/drupal/$DRUSH_DRUPAL_VERSION';
+$options['root'] = '/drupal/$DRUPAL_VERSION';

drush/settings.php

@@ -11,7 +11,7 @@ $databases['default']['default'] = array (
   'driver' => 'mysql',
 );
 
-if (file_exists("/drupal/$DRUSH_DRUPAL_VERSION/sites/$DRUSH_SITENAME/private/.docker.rerun.flag")) {
+if (file_exists("/drupal/$DRUPAL_VERSION/sites/$DRUSH_SITENAME/private/.docker.rerun.flag")) {
   $databases['default']['default']['password'] = null;
   print("The docker image has been updated. Please exit right now and rerun it!\n");
   exit;

prepare-enviroment.sh

@@ -24,7 +24,7 @@ mkdir -p /drupal/${DRUPAL_VERSION}/sites/${DRUSH_SITENAME}/
 find /mnt/site/ -mindepth 1 -maxdepth 1 -type d -exec ln -s {} /drupal/${DRUPAL_VERSION}/sites/${DRUSH_SITENAME}/ \;
 
 #copy settings.php to the final destination
-envsubst '$DRUSH_SITENAME$DRUSH_HOST$DRUSH_EGROUP$DRUSH_OWNER$DRUSH_EGROUP$DRUSH_USERNAME$DRUSH_PASSWORD$DRUSH_DATABASE$DRUSH_PORT$DRUSH_DRUPAL_VERSION$DRUPAL_VERSION' < /drush/settings.php > /drupal/${DRUPAL_VERSION}/sites/${DRUSH_SITENAME}/settings.php
+envsubst '$DRUSH_SITENAME$DRUSH_HOST$DRUSH_EGROUP$DRUSH_OWNER$DRUSH_EGROUP$DRUSH_USERNAME$DRUSH_PASSWORD$DRUSH_DATABASE$DRUSH_PORT$DRUPAL_VERSION' < /drush/settings.php > /drupal/${DRUPAL_VERSION}/sites/${DRUSH_SITENAME}/settings.php
 
 rm /drupal/${DRUPAL_VERSION}/sites/${DRUSH_SITENAME}/private/.docker.rerun.flag