$ git clone -n https://src.fedoraproject.org/rpms/rust-bootupd.git /var/lib/mock/f39-build-1588683-38228/root/chroot_tmpdir/scmroot/rust-bootupd
Cloning into '/var/lib/mock/f39-build-1588683-38228/root/chroot_tmpdir/scmroot/rust-bootupd'...
$ git fetch origin 879a8e7ff60aefbec35374dbb88b9952835b4683:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-bootupd
 * [new ref]         879a8e7ff60aefbec35374dbb88b9952835b4683 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 879a8e7 Update sources