@Override
	public String getDefaultMetaVariable() {
		return possibleValues.toString().replace(",", " |");
	}
An {@link OptionHandler} that scans a resource pattern for existing resources (using a single '*' wildcard) and
allows all String values <i>s</i> that would fit if that single wildcard was replaced by <i>s</i>.

<p>
Given that an option handler has to appear as an annotation parameter, expected usage is to sublcass this class,
provide the canonical 3 arg constructor to {@link OptionHandler} and pass the resource pattern as the 4th argument.
</p>

@author Eric Bottard
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/server/options/ResourcePatternScanningOptionHandler.java