$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gobject-introspection.git /var/lib/mock/f41-build-855343-167105/root/chroot_tmpdir/scmroot/rubygem-gobject-introspection
Cloning into '/var/lib/mock/f41-build-855343-167105/root/chroot_tmpdir/scmroot/rubygem-gobject-introspection'...
$ git fetch origin 368ac056a017e775bfa3fd34d2e881a6b9b5ee7c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gobject-introspection
 * [new ref]         368ac056a017e775bfa3fd34d2e881a6b9b5ee7c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 368ac05 4.2.3 entry