$ git clone -n https://src.fedoraproject.org/rpms/rubygem-tk.git /var/lib/mock/f45-build-35447-695/root/chroot_tmpdir/scmroot/rubygem-tk
Cloning into '/var/lib/mock/f45-build-35447-695/root/chroot_tmpdir/scmroot/rubygem-tk'...
$ git fetch origin f3bbea6ba52319ba2c87ab58af51ba29b9f38b3c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-tk
 * [new ref]         f3bbea6ba52319ba2c87ab58af51ba29b9f38b3c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f3bbea6 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild