$ git clone -n https://src.fedoraproject.org/rpms/rubygem-fog-core.git /var/lib/mock/f40-build-2033705-47834/root/chroot_tmpdir/scmroot/rubygem-fog-core
Cloning into '/var/lib/mock/f40-build-2033705-47834/root/chroot_tmpdir/scmroot/rubygem-fog-core'...
$ git fetch origin de2d0f4ded49b6ed1e65b6d020de0c39b9c40ded:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-fog-core
 * [new ref]         de2d0f4ded49b6ed1e65b6d020de0c39b9c40ded -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at de2d0f4 Update to fog-core 2.3.0.