Backport schema_changed.sh from EE which prints the diff if the schema is different

changelogs/unreleased/schema-changed-ee-backport.yml

+---
+title: Backport schema_changed.sh from EE which prints the diff if the schema is different
+merge_request: 21422
+author: Jasper Maes
+type: other

scripts/schema_changed.sh

-function schema_changed() {
-  if [[ ! -z `git diff --name-only -- db/schema.rb` ]]; then
-    echo "db/schema.rb after rake db:migrate:reset is different from one in the repository"
+#!/bin/sh
+
+schema_changed() {
+  if [ ! -z "$(git diff --name-only -- db/schema.rb)" ]; then
+    printf "db/schema.rb after rake db:migrate:reset is different from one in the repository"
+    printf "The diff is as follows:\n"
+    diff=$(git diff -p --binary -- db/schema.rb)
+    printf "%s" "$diff"
     exit 1
   else
-    echo "db/schema.rb after rake db:migrate:reset matches one in the repository"
+    printf "db/schema.rb after rake db:migrate:reset matches one in the repository"
   fi
 }