File _service of Package slhelpers

<services>
  <service name="tar_scm">
    <param name="url">https://github.com/jirislaby/slhelpers</param>
    <param name="scm">git</param>
    <param name="versionformat">%cd.%h</param>
  </service>
  <service name="recompress">
    <param name="file">_service:tar_scm:slhelpers-*.tar</param>
    <param name="compression">xz</param>
  </service>
  <service name="set_version"/>
</services>