Update pre-release script to allow for version changes

bin/pre-release.sh

@@ -4,9 +4,12 @@ set -e
 CURRENT_BRANCH_NAME=$(git rev-parse --abbrev-ref HEAD)
 BRANCH_NAME="pre-release-$CURRENT_BRANCH_NAME"
 
-# Check if there are files that need to be commited
-if [[ -n $(git status --porcelain) ]]; then
-  echo "⚠️ You have unstaged files, please commit these and then try again."
+# Check if there are unexpected changes. Changes to package.json and
+# package-lock.json files are expected as part of the pre-release process.
+changes="$(git status --porcelain -- ':!packages/govuk-frontend/package.json' ':!package-lock.json')"
+if [[ -n $changes ]]; then
+  echo "⚠ Unexpected changes in your working directory:"
+  echo "$changes"
   exit 1
 fi