Make sure there's only one attachments plugin enabled

plugins/database_attachments/composer.json

@@ -3,7 +3,7 @@
     "type": "roundcube-plugin",
     "description": "This plugin which provides database backed storage for temporary attachment file handling. The primary advantage of this plugin is its compatibility with round-robin dns multi-server Roundcube installations.",
     "license": "GPLv2",
-    "version": "1.1",
+    "version": "1.2",
     "authors": [
         {
             "name": "Aleksander Machniak",

plugins/database_attachments/database_attachments.php

@@ -1,9 +1,10 @@
 <?php
+
 /**
  * Database Attachments
  *
  * This plugin which provides database backed storage for temporary
- * attachment file handling.  The primary advantage of this plugin
+ * attachment file handling. The primary advantage of this plugin
  * is its compatibility with round-robin dns multi-server roundcube
  * installations.
  *
@@ -12,8 +13,25 @@
  * @author Ziba Scott <ziba@umich.edu>
  * @author Aleksander Machniak <alec@alec.pl>
  * @version @package_version@
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+if (class_exists('filesystem_attachments', false)) {
+    die("Configuration issue. There can be only one enabled plugin for attachments handling");
+}
+
 require_once INSTALL_PATH . 'plugins/filesystem_attachments/filesystem_attachments.php';
 
 class database_attachments extends filesystem_attachments

plugins/redundant_attachments/composer.json

@@ -3,7 +3,7 @@
     "type": "roundcube-plugin",
     "description": "This plugin provides a redundant storage for temporary uploaded attachment files. They are stored in both the database backend as well as on the local file system. It provides also memcache store as a fallback.",
     "license": "GPLv2",
-    "version": "1.0",
+    "version": "1.1",
     "authors": [
         {
             "name": "Aleksander Machniak",

plugins/redundant_attachments/redundant_attachments.php

@@ -1,4 +1,5 @@
 <?php
+
 /**
  * Redundant attachments
  *
@@ -31,6 +32,10 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+if (class_exists('filesystem_attachments', false)) {
+    die("Configuration issue. There can be only one enabled plugin for attachments handling");
+}
+
 require_once(RCUBE_PLUGINS_DIR . 'filesystem_attachments/filesystem_attachments.php');
 
 class redundant_attachments extends filesystem_attachments