add plugin uninstall trigger

docs/development/plugin-triggers.md

@@ -866,6 +866,21 @@ APP="$1"; IMAGE_TAG="$2"
 some code to remove a docker hub tag because it's not implemented in the CLI....
 ```
 
+### `uninstall`
+ - Description: Used to cleanup after itself.
+ - Invoked by: `dokku plugin:uninstall`
+ - Arguments: None
+ - Example:
+
+ ```shell
+ #!/usr/bin/env bash
+ # Cleanup up extra containers created
+
+ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+
+ docker rmi -f "${PLUGIN_IMAGE_DEPENDENCY}"
+ ```
+
 ### `update`
 
 - Description: Can be used to run plugin updates on a regular interval. You can schedule the invoker in a cron-task to ensure your system gets regular updates.

plugins/plugin/functions

@@ -70,6 +70,7 @@ uninstall_plugin() {
   local PLUGIN="$1"
   [[ -e $PLUGIN_CORE_AVAILABLE_PATH/$PLUGIN ]] && dokku_log_fail "Cannot uninstall a core plugin"
   [[ ! -e $PLUGIN_AVAILABLE_PATH/$PLUGIN ]] && dokku_log_fail "Plugin ($PLUGIN) is not currently installed"
+  plugn trigger uninstall
   plugn uninstall "$PLUGIN"
   dokku_log_info1_quiet "Plugin $PLUGIN uninstalled"
 }