content_migrate's field-module handling is hardcoded

If you look through content_migrate.module you'll see things like this:

/**
 * Implements hook_content_migrate_data_record_alter().
 *
 * Tweaks individual records in a field.
 */
function content_migrate_content_migrate_data_record_alter(&$record, $field, $instance) {

  module_load_include('inc', 'content_migrate', 'modules/content_migrate.filefield');
  content_migrate_filefield_data_record_alter($record, $field, $instance);

}

and then in modules/content_migrate.filefield.inc it has e.g.:

/**
 * Implements hook_content_migrate_data_record_alter().
 *
 * Tweaks individual records in a field.
 */
function content_migrate_filefield_data_record_alter(&$record, $field, $instance) {
....
}

The problem with this is that it hardcodes which functions are executed for which hooks, rather than the hooks system deciding what needs to be executed.

This means that right now text_content_migrate_data_record_alter() is never actually executed so #1913072: Single on/off checkbox labels lost when upgrading to D7 with content_migrate can't be fixed without fixing the module's architecture itself.

It shouldn't be very hard to fix this, but the module should never have been written this way in the first place.