Bug 31556 Export jar from Navigator view fails
(M5 build) In Navigator view (resource perspective), right-click on a src/ directory containing your sources, select export->jar file and the package selector opens with no resource selected (and finish button disabled); but it seems that the src/ dir is really selected, because if you re-select it in the window, it ends up with a "jar creation failed" and a lot of duplicate entries in the error log. If you try the same from the Projects view (Java browsing perspective), it works fine.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarPackageWizardPage.java
if (pageComplete)
			setErrorMessage(null);
	}
	
	/*
	 * Overrides method from WizardDataTransferPage
	 */
	protected boolean validateDestinationGroup() {
		if (fDestinationNamesCombo.getText().length() == 0) {
			 
			if (getErrorMessage() != null)
				setErrorMessage(null);
			if (getMessage() != null)
				setMessage(null);
			return false;
		}
		if (fJarPackage.getJarLocation().toString().endsWith("/")) { 
			setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.exportDestinationMustNotBeDirectory")); 
			fDestinationNamesCombo.setFocus();
			return false;
		}
		if (getWorkspaceLocation() != null && getWorkspaceLocation().isPrefixOf(fJarPackage.getJarLocation())) {
			int segments= getWorkspaceLocation().matchingFirstSegments(fJarPackage.getJarLocation());
			IPath path= fJarPackage.getJarLocation().removeFirstSegments(segments);
			IResource resource= ResourcesPlugin.getWorkspace().getRoot().findMember(path);
			if (resource != null && resource.getType() == IResource.FILE) {
				
				if (JarPackagerUtil.contains(JarPackagerUtil.asResources(fJarPackage.getElements()), (IFile)resource)) {
					setErrorMessage(JarPackagerMessages.getString("JarPackageWizardPage.error.cantExportJARIntoItself")); 
					return false;