$ git clone -n https://src.fedoraproject.org/rpms/jctools.git /var/lib/mock/f42-build-3347430-45004/root/chroot_tmpdir/scmroot/jctools
Cloning into '/var/lib/mock/f42-build-3347430-45004/root/chroot_tmpdir/scmroot/jctools'...
$ git fetch origin 291fb1dec3482417352cd2e32a39d146590a6e72:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jctools
 * [new ref]         291fb1dec3482417352cd2e32a39d146590a6e72 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 291fb1d Remove javadoc subpackage