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/internal/ui/packageview/SelectionTransferDropAdapter.java
return true;
			}	
			switch (showMoveDialog(ref)){
				case IDialogConstants.CANCEL_ID:
				 	setShowPreview(false);
					return false;
				case IDialogConstants.YES_ID:
					setShowPreview(false);
					return true;
				case PREVIEW_ID:		 
					setShowPreview(true);
					return true;
				default: 
					Assert.isTrue(false); 
					return false;
			}
		}
		
		private static int showMoveDialog(MoveRefactoring ref) {
			Shell shell= JavaPlugin.getActiveWorkbenchShell().getShell();
			final UpdateDialog dialog= new UpdateDialog(shell, ref);
			shell.getDisplay().syncExec(new Runnable() {
				public void run() {
					dialog.open();
				}
			});
			return dialog.getReturnCode();
		}
		
		private static class UpdateDialog extends Dialog {