$ git clone -n https://src.fedoraproject.org/rpms/php-sebastian-version6.git /var/lib/mock/f42-build-3224779-41162/root/chroot_tmpdir/scmroot/php-sebastian-version6
Cloning into '/var/lib/mock/f42-build-3224779-41162/root/chroot_tmpdir/scmroot/php-sebastian-version6'...
$ git fetch origin fef2cd0fde7714c93948150724d6f2f149461a3e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/php-sebastian-version6
 * [new ref]         fef2cd0fde7714c93948150724d6f2f149461a3e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fef2cd0 sources