$ git clone -n https://src.fedoraproject.org/rpms/rubygem-mime-types.git /var/lib/mock/f45-build-35051-693/root/chroot_tmpdir/scmroot/rubygem-mime-types
Cloning into '/var/lib/mock/f45-build-35051-693/root/chroot_tmpdir/scmroot/rubygem-mime-types'...
$ git fetch origin 1f83f02be101c7d3f3896aa9b56ff0c9e619273a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-mime-types
 * [new ref]         1f83f02be101c7d3f3896aa9b56ff0c9e619273a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 1f83f02 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild