Merge pull request #1867 from WickyNilliams/patch-1

Add note about key prop being excluded by cloneWithProps

docs/09.5-clone-with-props.md

@@ -11,3 +11,10 @@ In rare situations a component may want to change the props of a component that
 #### `ReactComponent React.addons.cloneWithProps(ReactComponent component, object? extraProps)`
 
 Do a shallow copy of `component` and merge any props provided by `extraProps`. Props are merged in the same manner as [`transferPropsTo()`](/react/docs/component-api.html#transferpropsto), so props like `className` will be merged intelligently.
+
+> Note:
+>
+> `cloneWithProps` does not transfer the `key` prop to the cloned component. If you wish to preserve the key, add it to the `extraProps` object:
+> ```js
+> var clonedComponent = cloneWithProps(originalComponent, { key : originalComponent.props.key });
+> ```