idea-config-repo/laf.xml

<application>
  <component name="LafManager" autodetect="false">
    <laf class-name="com.intellij.ide.ui.laf.darcula.DarculaLaf" themeId="4f556d32-83cb-4b8b-9932-c4eccc4ce3af" />
  </component>
</application>