Include metadata when using compositor File Output node?

I’ve been reading up a bit on Blender’s useful metadata that it puts into rendered images, but I can’t seem to find any way to make it include this information to files written by the File Output node. As far as I can see it will only write metadata to a render that comes from the Composite node. This is a bit of a nuisance when I am trying to render different layers separately using file output nodes, and want to refer back to info about them.

Can this be done or am I out of luck?