$ git clone -n https://src.fedoraproject.org/rpms/exim.git /var/lib/mock/f42-build-3426268-45168/root/chroot_tmpdir/scmroot/exim
Cloning into '/var/lib/mock/f42-build-3426268-45168/root/chroot_tmpdir/scmroot/exim'...
$ git fetch origin 797b90d3c0a68d35c2c3e57fd94ba06d0434f892:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/exim
 * [new ref]         797b90d3c0a68d35c2c3e57fd94ba06d0434f892 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 797b90d New version