Pull adds a compiler pass class that can rewrite the default form theme(s). Pass accepts from, to constructor arguments.
Pull does not engage this compiler pass in any way.

This is intended to

• allow Mapbender core to wrestle control over default form theming away from FOM and Mapbender Starter; the main issue here is that rolling out theming fixes across three repositories in a concerted fashion is complex and error prone
• improve project ability to model global theming changes as bundles

Example usage:
Place into any Bundle class's build method (MapbenderCoreBundle works fine):

$container->addCompilerPass(new RewriteFormThemeCompilerPass('FOMCoreBundle:Form:fields.html.twig', 'bootstrap_3_layout.html.twig'));

This makes every form in the entire Mapbender backend render in Bootstrap 3 theme. There are some layouting quirks with "extended collections", "region properties" etc. So this is not recommended for general use. It just proves that the replacement method works on a base level.