Bug 78317 Compare plug-in gets loaded by LocalHistoryActionGroup
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/compare/JavaHistoryAction.java
cu= ((IMember)input).getCompilationUnit();
			
		if (cu == null || !cu.exists())
			return null;
			
		
		cu= JavaModelUtil.toOriginal(cu);
			
		
		IFile file= (IFile) cu.getResource();
		if (file != null && file.exists())
			return file;
		return null;
	}
	
	final ITypedElement[] buildEditions(ITypedElement target, IFile file) {
		
		IFileState[] states= null;		
		
		try {
			states= file.getHistory(null);
		} catch (CoreException ex) {
			JavaPlugin.log(ex);
		}
		
		int count= 1;
		if (states != null)
			count+= states.length;
		ITypedElement[] editions= new ITypedElement[count];
		editions[0]= new ResourceNode(file);