Bug 78317 Compare plug-in gets loaded by LocalHistoryActionGroup
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/compare/JavaHistoryAction.java
/**
	 * Returns an IMember or null.
	 */
	final IMember getEditionElement(ISelection selection) {
		
		if (selection instanceof IStructuredSelection) {
			IStructuredSelection ss= (IStructuredSelection) selection;
			if (ss.size() == 1) {
				Object o= ss.getFirstElement();
				if (o instanceof IMember) {
					IMember m= (IMember) o;
					if (m.exists() && !m.isBinary() && JavaStructureCreator.hasEdition(m))
						return m;
				}
			}
		}
		return null;
	}
	
	final boolean isEnabled(IFile file) {
		if (file == null || ! file.exists())
			return false;
		if (fModifiesFile) {
			
			
			
			return true;
		}
		return true;
	}