$ git clone -n https://src.fedoraproject.org/rpms/rust-arcstr.git /var/lib/mock/f45-build-40111-768/root/chroot_tmpdir/scmroot/rust-arcstr
Cloning into '/var/lib/mock/f45-build-40111-768/root/chroot_tmpdir/scmroot/rust-arcstr'...
$ git fetch origin 96d663853aa462628042b27aa7594e1c5d37da0c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-arcstr
 * [new ref]         96d663853aa462628042b27aa7594e1c5d37da0c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 96d6638 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild