This would be intended for https://github.com/metabrainz/picard/pull/475 which displays search results within Picard rather than opening them in a web browser. In order to display the same results in both cases, we need an external way to pass &dismax=true through to the internal lucene query. This should probably remain undocumented, since it's not clear if it makes sense in the new SOLR-based project.