$ git clone -n https://src.fedoraproject.org/rpms/mpc.git /var/lib/mock/f39-build-2170388-51017/root/chroot_tmpdir/scmroot/mpc
Cloning into '/var/lib/mock/f39-build-2170388-51017/root/chroot_tmpdir/scmroot/mpc'...
$ git fetch origin c72f1f0b4d33212ed52c59edd2568e2d96aa0941:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/mpc
 * [new ref]         c72f1f0b4d33212ed52c59edd2568e2d96aa0941 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c72f1f0 Update to 0.35.