From 905b3028b47338f79eb208aa0c4227e72bcdd22b Mon Sep 17 00:00:00 2001
From: Jose Diaz-Gonzalez <josegonzalez@users.noreply.github.com>
Date: Tue, 5 Jul 2016 02:16:37 -0400
Subject: [PATCH] Add an example plugin trigger for cache busting Dockerfile
 builds

Closes #2288
---
 docs/development/plugin-triggers.md | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/docs/development/plugin-triggers.md b/docs/development/plugin-triggers.md
index 1313bcb03..c70074fe2 100644
--- a/docs/development/plugin-triggers.md
+++ b/docs/development/plugin-triggers.md
@@ -201,10 +201,23 @@ echo 'derp.dkr.ecr.us-east-1.amazonaws.com'
 
 ```shell
 #!/usr/bin/env bash
-
+# Sets a docker build-arg called CACHEBUST which can be used
+# to bust cache at any arbitrary point in a Dockerfile build
 set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 
-# TODO
+cache-bust-build-arg() {
+  declare desc="dockerfile cache busting plugin trigger"
+  local STDIN=$(cat)
+  local APP="$1" IMAGE_SOURCE_TYPE="$2"
+  local output=""
+
+  if [[ "$IMAGE_SOURCE_TYPE" == "dockerfile" ]]; then 
+    output=" --build-arg CACHEBUST=$(date +%s)"
+  fi
+  echo -n "$STDIN$output"
+}
+
+cache-bust-build-arg "$@"
 ```
 
 ### `docker-args-deploy`