private String determineTapChannel(ModuleDescriptor descriptor) {
		String sourceChannelName = descriptor.getSourceChannelName();
		return (sourceChannelName != null && sourceChannelName.startsWith(TAP_CHANNEL_PREFIX)) ?
				sourceChannelName.substring(TAP_CHANNEL_PREFIX.length()) : null;
	}
Determine whether the provided descriptor has a tap channel as its "source", and if so return the unqualified tap
channel name. If not, return {@code null}.

@param descriptor ModuleDescriptor whose source channel is checked
@return unqualified tap channel name or {@code null}
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/server/container/DeploymentListener.java