$ git clone -n https://src.fedoraproject.org/rpms/libnbd.git /var/lib/mock/f41-build-851919-166142/root/chroot_tmpdir/scmroot/libnbd
Cloning into '/var/lib/mock/f41-build-851919-166142/root/chroot_tmpdir/scmroot/libnbd'...
$ git fetch origin a8fffa93cc92de3d69e3651af85dc54617571a46:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libnbd
 * [new ref]         a8fffa93cc92de3d69e3651af85dc54617571a46 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a8fffa9 New upstream development version 1.21.4