$ git clone -n https://src.fedoraproject.org/rpms/rust-portable-atomic-util.git /var/lib/mock/f39-build-1967104-43295/root/chroot_tmpdir/scmroot/rust-portable-atomic-util
Cloning into '/var/lib/mock/f39-build-1967104-43295/root/chroot_tmpdir/scmroot/rust-portable-atomic-util'...
$ git fetch origin fce729baf28d5f133d1f80b17e443c6b64fc5101:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-portable-atomic-util
 * [new ref]         fce729baf28d5f133d1f80b17e443c6b64fc5101 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fce729b Initial import (#2242768)