Bug 29698 drag and drop of java files between packages in package explorer doesn't work
the <preview> <ok> <cancel> dialog shows up, but <ok> has the same effect as <cancel> and <preview> would only show movements of files and no changes in imports of other java files. on <ok> in the preview it only moves the file(s) (as indicated ) without changing referencing imports.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/refactoring/RenameSupport.java
* 
	 * @return the result of the light weight precondition checking.
	 * 
	 * @throws if an unexpected exception occurs while performing the checking.
	 * 
	 * @see #openDialog(Shell)
	 * @see #perform(Shell, IRunnableContext)
	 */
	public IStatus preCheck() throws CoreException {
		ensureChecked();
		if (fPreCheckStatus.hasFatalError())
			return fPreCheckStatus.getFirstEntry(RefactoringStatus.FATAL).asStatus();
		else
			return new Status(IStatus.OK, JavaPlugin.getPluginId(), 0, "", null);
	}
	/**
	 * Opens the refactoring dialog for this rename support. 
	 * 
	 * @param parent a shell used as a parent for the refactoring dialog.
	 * @throws CoreException if an unexpected exception occurs while opening the
	 * dialog.
	 */
	public void openDialog(Shell parent) throws CoreException {
		ensureChecked();
		if (fPreCheckStatus.hasFatalError()) {
			showInformation(parent, fPreCheckStatus);
			return; 
		}
		fSupport.rename(parent, fElement);
	}