Bug 80833 [Import/Export] Import exisiting should pre-check for project already in workspace
While it is good that it lets you import projects in the default workspace location, it should not let you select projects that already exist in the workspace (since importing such a project will fail). When searching for .project files in the file system, it could use IWorkspaceRoot.findFilesForLocation followed by checking IFile.exists() to filter out .project files for existing projects.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardProjectsImportPage.java
*/
	private boolean createExistingProject(final ProjectRecord record, IProgressMonitor monitor) throws InvocationTargetException, InterruptedException {
		String projectName = record.getProjectName();
		final IWorkspace workspace = ResourcesPlugin.getWorkspace();
		final IProject project = workspace.getRoot().getProject(projectName);
		if (record.description == null) {
			record.description = workspace.newProjectDescription(projectName);
			IPath locationPath = new Path(record.projectSystemFile
					.getAbsolutePath());
			
			
			
			if (Platform.getLocation().isPrefixOf(locationPath))
				record.description.setLocation(null);
			else
				record.description.setLocation(locationPath);
		} else
			record.description.setName(projectName);
		if (record.projectArchiveFile != null) {
			
			ArrayList fileSystemObjects = new ArrayList();
			getFilesForProject(fileSystemObjects, record.provider,
					record.parent);
			record.provider.setStrip(record.level);
			ImportOperation operation = new ImportOperation(project
					.getFullPath(), record.provider.getRoot(), record.provider,
					this, fileSystemObjects);
			operation.setContext(getShell());
			operation.run(monitor);
			return true;