packages/netlify-cms-core/src/lib/stringTemplate.js
function getExplicitFieldReplacement(key, data) {
  if (!key.startsWith(FIELD_PREFIX)) {
    return;
  }
  const fieldName = key.substring(FIELD_PREFIX.length);
  return data.get(fieldName, '');
}
function getExplicitFieldReplacement(key, data) {
  if (!key.startsWith(FIELD_PREFIX)) {
    return;
  }
  const fieldName = key.substring(FIELD_PREFIX.length);
  return data.get(fieldName, '');
}
function getExplicitFieldReplacement ( key , data ) { if ( ! key . startsWith ( FIELD_PREFIX ) ) { return ; } const fieldName = key . substring ( FIELD_PREFIX . length ) ; return data . get ( fieldName , '' ) ; }
Allow `fields.` prefix in placeholder to override built in replacements like "slug" and "year" with values from fields of the same name.
Allow fields . prefix in placeholder to override built in replacements like slug and year with values from fields of the same name .