$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rack-cache.git /var/lib/mock/f45-build-35241-694/root/chroot_tmpdir/scmroot/rubygem-rack-cache
Cloning into '/var/lib/mock/f45-build-35241-694/root/chroot_tmpdir/scmroot/rubygem-rack-cache'...
$ git fetch origin 045cbe3c490f9592f1a304a83045f605c6906c2c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rack-cache
 * [new ref]         045cbe3c490f9592f1a304a83045f605c6906c2c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 045cbe3 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild