title: Can some clarify usage of <include> and <merge>
body: <p>I just need someone to tell me if I understood correctly when to use <code>&lt;include&gt;</code> and when <code>&lt;merge&gt;</code>. </p>
  
  <p>So, I make a header layout which I want to include into some other XML layout: </p>
  
  <pre><code>&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"&gt;
  
      &lt;TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Header text" /&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>And I include it into some other XML this way (which is pretty basic):</p>
  
  <pre><code>&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="fill_parent"
      android:layout_height="fill_parent"&gt;
  
      &lt;include
          android:id="@+id/header"
          layout="@layout/top"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content" /&gt;
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>This will work well, no issue about it. But in order to optimize the code, I have to use <code>&lt;merge&gt;</code> in the layout which gets included. So the <code>top layout</code> should not have a tag <code>&lt;LinearLayout&gt;</code> but it must look like this:</p>
  
  <pre><code>&lt;merge xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Header text" /&gt;
  &lt;/merge&gt;
  </code></pre>
  
  <p>Have I understood this correctly?</p>