Bug 330553 [Import/Export] Importing a project that exists in workspace location merges the contents
(1) Create a project in the default location (2) Export it to an archive (3) Delete it (but don't choose the option to delete from disk) (4) Make some changes in the <workspace root>/<project> directory (4) Import the archive you exported in step 2 This results in files from both the archive and directory. If the directory already has a file thats available in the archive, then it doesn't modify it. Ideally we shouldn't be allowing the import at all.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardProjectsImportPage.java
if (t instanceof CoreException) {
				status = ((CoreException) t).getStatus();
			} else {
				status = new Status(IStatus.ERROR,
						IDEWorkbenchPlugin.IDE_WORKBENCH, 1, message, t);
			}
			ErrorDialog.openError(getShell(), message, null, status);
			return false;
		}
		ArchiveFileManipulations.closeStructureProvider(structureProvider,
				getShell());
		
		addToWorkingSets();
		
		return true;
	}
	List createdProjects;
	
	private void addToWorkingSets() {
		
		IWorkingSet[] selectedWorkingSets = workingSetGroup.getSelectedWorkingSets();
		if(selectedWorkingSets == null || selectedWorkingSets.length == 0)
			return; 
		IWorkingSetManager workingSetManager = PlatformUI.getWorkbench().getWorkingSetManager();
		for (Iterator i = createdProjects.iterator(); i.hasNext();) {
			IProject project = (IProject) i.next();
			workingSetManager.addToWorkingSets(project, selectedWorkingSets);
		}
	}
	/**