Add verify docker prefix (#90)

* Add verify docker prefix

* Update args

* Fix the order

hack/verify-docker-prefix.sh

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+
+file=$1
+
+cp ${file} ${file}.bak
+
+cat ${file} | grep docker.io | grep library | sed 's#docker.io/library/#docker.io/#' >>${file}.bak
+
+cat ${file} | grep -e "docker\.io/\w\+:\|docker\.io/\w\+$" | sed 's#docker.io/#docker.io/library/#' >>${file}.bak
+
+$(dirname "${BASH_SOURCE}")/fmt.sh ${file}.bak
+
+result=$(diff ${file} ${file}.bak)
+
+if [[ "${result}" != "" ]]; then
+    echo "Usually docker.io/* and docker.io/library/* appear in pairs "
+    echo "Please run following command to fix the issue:"
+    echo "cat <<EOF >> ${file}"
+    echo "${result}" | grep "^>" | sed 's/^>\s\+//'
+    echo "EOF"
+    echo "./hack/fmt.sh ${file}"
+
+    exit 1
+fi
+
+rm ${file}.bak