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
files.add(file);
				
				
				return true;
			}
		}
		
		for (int i = 0; i < contents.length; i++) {
			if (contents[i].isDirectory())
				if (!contents[i].getName().equals(
						IDEApplication.METADATA_FOLDER))
					collectProjectFilesFromDirectory(files, contents[i],
							monitor);
		}
		return true;
	}
	/**
	 * Collect the list of .project files that are under directory into files.
	 * 
	 * @param files
	 * @param monitor
	 *            The monitor to report to
	 * @return boolean <code>true</code> if the operation was completed.
	 */
	private boolean collectProjectFilesFromProvider(Collection files,
			ILeveledImportStructureProvider provider, Object entry, int level,
			IProgressMonitor monitor) {
		if (monitor.isCanceled())
			return false;
		monitor.subTask(NLS.bind(