Update bin/test-changed-exercise

Co-authored-by: Kah Goh <[email protected]>

Author: jagdish-15

bin/test-changed-exercise

@@ -8,7 +8,7 @@ BASE_BRANCH=${GITHUB_BASE_REF:-main}
 git fetch origin "$BASE_BRANCH"
 
 # Compute merge base
-MERGE_BASE=$(git merge-base HEAD origin/$BASE_BRANCH)
+MERGE_BASE=$(git merge-base HEAD origin/"$BASE_BRANCH")
 
 # Get changed files relative to merge base
 changed_files=$(git diff --name-only "$MERGE_BASE" HEAD)