Entity list operations can now be declared and altered by any module

Any module can now declare and alter entity (list) operations for entities that belong to another module by implementing hook_entity_operation() and hook_entity_operation_alter() respectively, as long as the entity type's list controller extends \Drupal\Core\Entity\EntityListController or invokes this hook itself explicitly.

Until now, declaring additional operations had to be done by implementing hook_entity_operation_alter(), which only worked for some lists and did not work if you did not want to render the operations as a dropbutton.

Adding a new operation:

/**
 * Implements hook_entity_operation().
 */
function foo_entity_operation(EntityInterface $entity) {
  $operations = array();
  if (\Drupal::currentUser->hasPermission('foo-operation') {
    $operations['foo-operation'] = array(
      'title' => t('Foo this entity'),
      'weight' => 15,
    ) + $entity->urlInfo('foo-operation');
  }

  return $operations;
}

Altering an existing operation:

/**
 * Implements hook_entity_operation_alter().
 */
function foo_entity_operation_alter(array &$operations, \Drupal\Core\Entity\EntityInterface $entity) {
  $uri = $entity->uri();
  $operations['translate']['title'] = t('Translate @entity_type', array(
    '@entity_type' => $entity->getEntityType()->getLabel(),
  ));
}

See Entity listing pages can be provided by a list controller for the original change notice on list controllers.