$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rack-session.git /var/lib/mock/f45-build-35224-694/root/chroot_tmpdir/scmroot/rubygem-rack-session
Cloning into '/var/lib/mock/f45-build-35224-694/root/chroot_tmpdir/scmroot/rubygem-rack-session'...
$ git fetch origin 886eaf4557e8f1ce2321150f08990cfec261b79d:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rack-session
 * [new ref]         886eaf4557e8f1ce2321150f08990cfec261b79d -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 886eaf4 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild