Jenkins SCM with ref repos

        checkout([
            $class: 'GitSCM',
            branches: scm.branches,
            doGenerateSubmoduleConfigurations: false,
            extensions: scm.extensions + [
                [
                    $class: 'SubmoduleOption',
                    disableSubmodules: false,
                    parentCredentials: true,
                    recursiveSubmodules: false,
                    reference: '/cache/submodules',
                    trackingSubmodules: false
                ], [
                    $class: 'CloneOption',
                    depth: 50,
                    noTags: false,
                    reference: '/cache/repo',
                    shallow: false
                ]
            ],
            submoduleCfg: [],
            userRemoteConfigs: scm.userRemoteConfigs
        ])