title: What does ext.kotlin_version = '+' mean in Build.gradle?
body: <p>The following code is from <a href="https://github.com/android/camera/blob/master/CameraXBasic/build.gradle" rel="noreferrer">https://github.com/android/camera/blob/master/CameraXBasic/build.gradle</a></p>
  
  <p>What does <code>ext.kotlin_version = '+'</code> mean in Build.gradle?</p>
  
  <p><strong>Build.gradle</strong></p>
  
  <pre><code>buildscript {
      // Top-level variables used for versioning
      ext.kotlin_version = '+'
      ext.java_version = JavaVersion.VERSION_1_8
  
      repositories {
          google()
          jcenter()
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.4.1'
          classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
          classpath "androidx.navigation:navigation-safe-args-gradle-plugin:2.0.0"
  
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
      }
  }
  </code></pre>
  
  <p><strong>Normal Code</strong></p>
  
  <pre><code>buildscript {
      ext.kotlin_version = '1.3.41'
      ext.anko_version = '0.10.8'
  
      repositories {
          google()
          jcenter()
  
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.4.1'
          classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
      }
  }
  </code></pre>