template.hbs

{{input class="checkbox-input" type="checkbox" name="hasRootDir" checked=hasRootDir}}
<label>My source directory is not at the checkout root</label>
{{#if hasRootDir}}
  <div>
    {{input
      class="text-input root-dir"
      placeholder="Enter your source directory path relative to the checkout URL (eg: src)"
      value=rootDir
      key-up=updateRootDir
    }}
  </div>
{{/if}}