Update docs for ktlint integration

docs/supported-tools.md

@@ -10,9 +10,7 @@ Tool | Java | Android<br/>(Java) | Kotlin | Android<br/>(Kotlin)
 [`FindBugs`](http://findbugs.sourceforge.net/) | :white_check_mark: | :white_check_mark: | — | —
 [`Detekt`](https://github.com/arturbosch/detekt) | — | — | :white_check_mark: | :white_check_mark:
 [`Android Lint`](https://developer.android.com/studio/write/lint.html) | — | :white_check_mark:️ | — | :white_check_mark:️
-[`KtLint`\*](https://github.com/shyiko/ktlint) | — | — | ✖️ | ✖️
-
-_\* Not supported [yet](https://github.com/novoda/gradle-static-analysis-plugin/issues?q=is%3Aopen+is%3Aissue+label%3A%22new+tool%22)_
+[`KtLint`](https://github.com/shyiko/ktlint) | — | — | :white_check_mark:️ | :white_check_mark:️
 
 For additional informations and tips on how to obtain advanced behaviours with the plugin and its tools, please refer to the
 [advanced usage](advanced-usage.md) page.
@@ -25,7 +23,7 @@ For additional informations and tips on how to obtain advanced behaviours with t
    * [PMD](tools/pmd.md)
    * [Findbugs](tools/findbugs.md)
    * [Android Lint](tools/android_lint.md)
-   * KtLint — _COMING SOON_
+   * [KtLint](tools/ktlint.md)
  * [Example configurations](#example-configurations)
 
 ---
@@ -42,7 +40,9 @@ staticAnalysis {
     checkstyle {}
     pmd {}
     findbugs {}
+    lintOptions {}
     detekt {}
+    ktlint {}
 }
 ```
 

docs/tools/ktlint.md

@@ -0,0 +1,58 @@
+# ktlint
+[Ktlint](https://github.com/shyiko/ktlint) is a linter for Kotlin with a built-in formatter. It does not support Java. Adding 
+this tool only makes sense when you have Kotlin sources in your project. In fact, it will fail to run if you have 0 Kotlin
+files.
+
+## Table of contents
+ * [IMPORTANT: setup Ktlint](#important-setup-ktlint)
+ * [Configure Ktlint](#configure-ktlint)
+---
+
+## IMPORTANT: setup Ktlint
+
+Unlike the other tools, the plugin **won't automatically add Ktlint** to your project. If you forget to do it, the plugin will 
+fail the build with an error.
+
+In order to integrate Ktlint easily we choose to use the [Ktlint Gradle plugin](https://github.com/JLLeitschuh/ktlint-gradle/).
+This plugin has a very good understanding of Android source sets and build flavors. You can refer to the
+[official documentation](https://github.com/JLLeitschuh/ktlint-gradle/#how-to-use) for further details.
+
+Note that you should _not_ add the `ktlint` closure to your `build.gradle`s, unlike what the official documentation says. The 
+`ktlint` closure in the `staticAnalysis` configuration gets applied to all Kotlin modules automatically.
+
+In most common cases, adding Ktlint to a project boils down to these simple steps:
+
+ 1. Add this statement to your root `build.gradle` project (change the version according to your needs):
+    ```gradle
+    plugins {
+        id 'org.jlleitschuh.gradle.ktlint' version '5.0.0'
+        // ...
+    }
+    ```
+ 2. Add this statement to each Kotlin project's `build.gradle`s:
+    ```gradle
+    plugins {
+        id 'org.jlleitschuh.gradle.ktlint'
+        // ...
+    }
+    ```
+
+## Configure Ktlint
+
+Unlike other tools, Ktlint does not offer much configuration. By default, it applies 
+[Kotlin style guide](https://kotlinlang.org/docs/reference/coding-conventions.html) or 
+[Android Kotlin style guide](https://android.github.io/kotlin-guides/style.html).
+
+To use Android style guide: 
+
+```gradle
+ktlint {
+    android true
+}
+```
+
+For other configuration options and adding custom rules, refer to the 
+[official guide](https://github.com/JLLeitschuh/ktlint-gradle/#configuration).
+
+**Note:** Failures and threshold detection is handled by Static Analysis plugin. That is why `ignoreFailures = true` is set by 
+the plugin. Please do not manually override `ignoreFailures` property.