$ git clone -n https://src.fedoraproject.org/rpms/rubygem-cairo-gobject.git /var/lib/mock/f41-build-855232-167090/root/chroot_tmpdir/scmroot/rubygem-cairo-gobject
Cloning into '/var/lib/mock/f41-build-855232-167090/root/chroot_tmpdir/scmroot/rubygem-cairo-gobject'...
$ git fetch origin 115f7d08b985463c43d91959b8a3e377be5613a0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-cairo-gobject
 * [new ref]         115f7d08b985463c43d91959b8a3e377be5613a0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 115f7d0 4.2.3 entry