Missing support for Firebase App Indexing (android lint)

Actually there are 2 ways to deal with 'app is not indexable by google' problem.

1. Add deep link into the app as described above.

2. Simply disable lint warning. Sometimes app is not published to Google Play so deep links will not be needed, etc:

   android {
   defaultConfig {
   // something
   }
   lintOptions {
   disable 'GoogleAppIndexingWarning'
   baseline file("lint-baseline.xml")
   }
   }
   

I found out how to access the "Issue Explanation". I need to hover over an inspection error to display the full issue explanation inline (and pressing Ctrl-F1)

so the keyword I am missing is "deep links"!

The following is the android developer page to do deep links "To enable Google to crawl your app content and allow users to enter your app from search results"

http://developer.android.com/training/app-indexing/deep-linking.html

the following is the code snippet on how to do a deep link. I got no idea how Google can crawl my app just by adding it though...

<activity
    android:name="com.example.android.GizmosActivity"
    android:label="@string/title_gizmos" >
    <intent-filter android:label="@string/filter_title_viewgizmos">
        <action android:name="android.intent.action.VIEW" />
        <category android:name="android.intent.category.DEFAULT" />
        <category android:name="android.intent.category.BROWSABLE" />
        <!-- Accepts URIs that begin with "http://www.example.com/gizmos” -->
        <data android:scheme="http"
              android:host="www.example.com"
              android:pathPrefix="/gizmos" />
        <!-- note that the leading "/" is required for pathPrefix-->
        <!-- Accepts URIs that begin with "example://gizmos”
        <data android:scheme="example"
              android:host="gizmos" />
        -->
    </intent-filter>
</activity>

there is also a note which says

Note: Intent filters may only contain a single data element for a URI pattern. 
Create separate intent filters to capture additional URI patterns.

You can remove the warning by adding the below code in <intent-filter> inside <activity>

        <action android:name="android.intent.action.VIEW" />

If you want disable this warning until your application development completes or if you don't have any web URL to add, add this line in your AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
          xmlns:tools="http://schemas.android.com/tools"
          package="com.example.yourappname">

   <application
       ...
       ...
       tools:ignore="GoogleAppIndexingWarning">

          ....

   </application>

</manifest>