$ git clone -n https://src.fedoraproject.org/rpms/rubygem-msgpack.git /var/lib/mock/f45-build-35138-693/root/chroot_tmpdir/scmroot/rubygem-msgpack
Cloning into '/var/lib/mock/f45-build-35138-693/root/chroot_tmpdir/scmroot/rubygem-msgpack'...
$ git fetch origin 06936cd5401cf52f803548aae1a46100e15555ba:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-msgpack
 * [new ref]         06936cd5401cf52f803548aae1a46100e15555ba -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 06936cd Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild