use a file instead of checking empty dir (more atomic)

start.sh

@@ -23,7 +23,7 @@ sed -e "s/##MYSQL_DATABASE/${MYSQL_DATABASE}/" \
     -e "s/##NONCE_SALT/$(pwgen -1cns 64)/" \
     /app/code/wp-config.php.template > /run/wordpress/wp-config.php # sed -i seems to destroy symlink
 
-if [[ -z "$(ls -A /app/data)" ]]; then
+if [[ ! -f "/app/data/.dbsetup" ]]; then
     echo "Copying wp-content files on first run"
     mkdir -p /app/data/wp-content/mu-plugins
     cp -r /app/code/wp-content-vanilla/* /app/data/wp-content/
@@ -49,6 +49,8 @@ if [[ -z "$(ls -A /app/data)" ]]; then
     unzip -d /app/data/wp-content/mu-plugins/ /app/code/authLdap.zip
     mv /app/data/wp-content/mu-plugins/authLdap-*/* /app/data/wp-content/mu-plugins/
     rm -rf /app/data/wp-content/mu-plugins/authLdap-*/
+
+    touch "/app/data/.dbsetup"
 else
     # Update wordpress
     echo "Updating wordpress database"