Bug 13799 JAR exporter exports class files from output folder
There was a problem with the output folder not being detected as such.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
}
	}
	public void singleRun(IProgressMonitor progressMonitor) throws InvocationTargetException, InterruptedException {
		try {
			if (!preconditionsOK())
				throw new InvocationTargetException(null, JarPackagerMessages.getString("JarFileExportOperation.jarCreationFailedSeeDetails")); 
			int totalWork= countSelectedElements();
			if (!isAutoBuilding() && fJarPackage.isBuildingIfNeeded()) {
				int subMonitorTicks= totalWork/10;
				totalWork += subMonitorTicks;
				progressMonitor.beginTask("", totalWork); 
				SubProgressMonitor subProgressMonitor= new SubProgressMonitor(progressMonitor, subMonitorTicks, SubProgressMonitor.PREPEND_MAIN_LABEL_TO_SUBTASK);
				buildProjects(subProgressMonitor);
			} else
				progressMonitor.beginTask("", totalWork); 
						
			fJarWriter= fJarPackage.createJarWriter(fParentShell);
			exportSelectedElements(progressMonitor);
			if (getStatus().getSeverity() != IStatus.ERROR) {
				progressMonitor.subTask(JarPackagerMessages.getString("JarFileExportOperation.savingFiles")); 
				saveFiles();
			}
		} catch (IOException ex) {
			String message= JarPackagerMessages.getFormattedString("JarFileExportOperation.unableToCreateJarFle",  ex.getLocalizedMessage()); 
			addError(message, ex);
			throw new InvocationTargetException(ex, message);
		} catch (CoreException ex) {
			String message= JarPackagerMessages.getFormattedString("JarFileExportOperation.unableToCreateJarFileDueToInvalidManifest", ex.getLocalizedMessage()); 
			addError(message, ex);
			throw new InvocationTargetException(ex, message);