$ git clone -n https://src.fedoraproject.org/rpms/rust-arbitrary.git /var/lib/mock/f45-build-40104-768/root/chroot_tmpdir/scmroot/rust-arbitrary
Cloning into '/var/lib/mock/f45-build-40104-768/root/chroot_tmpdir/scmroot/rust-arbitrary'...
$ git fetch origin e149cf332fb6ba21f87905cc5a21760c392a6645:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-arbitrary
 * [new ref]         e149cf332fb6ba21f87905cc5a21760c392a6645 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e149cf3 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild