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
*
	 *	@return java.lang.String
	 */
	protected String getDestinationValue() {
		String destinationText= fDestinationNamesCombo.getText().trim();
		if (destinationText.indexOf('.') < 0)
			destinationText += getOutputSuffix();
		return destinationText;
	}
	/**
	 *	Answer the string to display in self as the destination type
	 *
	 *	@return java.lang.String
	 */
	protected String getDestinationLabel() {
		return JarPackagerMessages.getString("JarPackageWizardPage.destination.label"); 
	}
	/**
	 *	Answer the suffix that files exported from this wizard must have.
	 *	If this suffix is a file extension (which is typically the case)
	 *	then it must include the leading period character.
	 *
	 *	@return java.lang.String
	 */
	protected String getOutputSuffix() {
		return "." + JarPackagerUtil.JAR_EXTENSION; 
	}
	/**
	 * Returns an iterator over this page's collection of currently-specified 
	 * elements to be exported. This is the primary element selection facility