framework/console/controllers/BaseMigrateController.php
protected function includeMigrationFile($class)
    {
        $class = trim($class, '\\');
        if (strpos($class, '\\') === false) {
            if (is_array($this->migrationPath)) {
                foreach ($this->migrationPath as $path) {
                    $file = $path . DIRECTORY_SEPARATOR . $class . '.php';
                    if (is_file($file)) {
                        require_once $file;
                        break;
                    }
                }
            } else {
                $file = $this->migrationPath . DIRECTORY_SEPARATOR . $class . '.php';
                require_once $file;
            }
        }
    }
protected function includeMigrationFile($class)
    {
        $class = trim($class, '\\');
        if (strpos($class, '\\') === false) {
            if (is_array($this->migrationPath)) {
                foreach ($this->migrationPath as $path) {
                    $file = $path . DIRECTORY_SEPARATOR . $class . '.php';
                    if (is_file($file)) {
                        require_once $file;
                        break;
                    }
                }
            } else {
                $file = $this->migrationPath . DIRECTORY_SEPARATOR . $class . '.php';
                require_once $file;
            }
        }
    }
Includes the migration file for a given migration class name.

This function will do nothing on namespaced migrations, which are loaded by
autoloading automatically. It will include the migration file, by searching
[[migrationPath]] for classes without namespace.
@param string $class the migration class name.
@since 2.0.12