added example cache purge script

installation/nginx-cache-purge.example

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+# A simple Bash script to delete an media from the Nginx cache.
+
+SCRIPTNAME=${0##*/}
+
+# NGINX cache directory 
+CACHE_DIRECTORY="/tmp/pleroma-media-cache"
+
+function get_cache_files() {
+    local max_parallel=${3-16}
+    find $2 -maxdepth 1 -type d | xargs -P $max_parallel -n 1 grep -ERl "^KEY:.*$1" | sort -u
+}
+
+function purge_item() {
+  local cache_files
+  cache_files=$(get_cache_files "$1" "$2")
+
+  if [ -n "$cache_files" ]; then
+    for i in $cache_files; do
+      [ -f $i ] || continue
+      echo "Deleting $i from $2."
+      rm $i
+    done
+  else
+    echo "$1 is not cached."
+  fi  
+}
+
+function purge() {
+  for url in "$@"
+  do
+    echo "$SCRIPTNAME delete $url from cache ($CACHE_DIRECTORY)"
+    purge_item $url $CACHE_DIRECTORY
+  done
+
+}
+
+purge $1