$ git clone -n https://src.fedoraproject.org/rpms/libgcroots.git /var/lib/mock/f45-build-16210-483/root/chroot_tmpdir/scmroot/libgcroots
Cloning into '/var/lib/mock/f45-build-16210-483/root/chroot_tmpdir/scmroot/libgcroots'...
$ git fetch origin 1ebd806ca266d5bd597ca0a857e98aad100a149e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/libgcroots
 * [new ref]         1ebd806ca266d5bd597ca0a857e98aad100a149e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1ebd806 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild