$ git clone -n https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/rubygem-childprocess.git /var/lib/mock/f41-build-3156341-40708/root/chroot_tmpdir/scmroot/rubygem-childprocess
Cloning into '/var/lib/mock/f41-build-3156341-40708/root/chroot_tmpdir/scmroot/rubygem-childprocess'...
$ git fetch origin 1968f2d115b6b2ae693d9a6959b8a98c1c89e0b3:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/u2fsdgvkx1/rpms/rubygem-childprocess
 * [new ref]         1968f2d115b6b2ae693d9a6959b8a98c1c89e0b3 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1968f2d add riscv64