Add checkstyle configuration and apply to all modules

bramble-api/build.gradle

@@ -5,6 +5,7 @@ targetCompatibility = 1.8
 apply plugin: 'ru.vyarus.animalsniffer'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
+apply plugin: 'checkstyle'
 
 dependencies {
 	implementation "com.google.dagger:dagger:$dagger_version"

bramble-core/build.gradle

@@ -7,6 +7,7 @@ apply plugin: 'idea'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
 apply from: '../dagger.gradle'
+apply plugin: 'checkstyle'
 
 dependencies {
 	implementation project(path: ':bramble-api', configuration: 'default')

bramble-java/build.gradle

@@ -6,6 +6,7 @@ apply plugin: 'idea'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
 apply from: '../dagger.gradle'
+apply plugin: 'checkstyle'
 
 configurations {
 	tor

briar-android/build.gradle

@@ -1,6 +1,10 @@
 apply plugin: 'com.android.application'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
+apply plugin: 'checkstyle'
+// Need to manually apply this as the Java plugin is not applied to this module hence this is not
+// done automatically.
+apply from: "${rootProject.rootDir}/gradle/checkstyle.gradle"
 
 def getStdout = { command, defaultValue ->
 	def stdout = new ByteArrayOutputStream()

briar-api/build.gradle

@@ -5,6 +5,7 @@ targetCompatibility = 1.8
 apply plugin: 'ru.vyarus.animalsniffer'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
+apply plugin: 'checkstyle'
 
 dependencies {
 	implementation project(path: ':bramble-api', configuration: 'default')

briar-core/build.gradle

@@ -7,6 +7,7 @@ apply plugin: 'idea'
 apply plugin: 'witness'
 apply from: 'witness.gradle'
 apply from: '../dagger.gradle'
+apply plugin: 'checkstyle'
 
 dependencies {
 	implementation project(path: ':briar-api', configuration: 'default')

config/checkstyle/checkstyle.xml

@@ -0,0 +1,19 @@
+<!DOCTYPE module PUBLIC
+          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+          "https://checkstyle.org/dtds/configuration_1_3.dtd">
+<module name="Checker">
+  <property name="tabWidth" value="4"/>
+  <property name="charset" value="UTF-8"/>
+  <module name="LineLength">
+    <property name="fileExtensions" value="java"/>
+    <property name="max" value="1000"/>
+    <property name="ignorePattern" value="^package.*|^import.*|a href|href|http://|https://|ftp://"/>
+  </module>
+  <module name="TreeWalker">
+    <module name="RegexpSinglelineJava">
+      <property name="format" value="^\t* +\t*\S"/>
+      <property name="message" value="Line has leading space characters; indentation should be performed with tabs only."/>
+      <property name="ignoreComments" value="true"/>
+    </module>
+  </module>
+</module>

gradle/checkstyle.gradle

@@ -0,0 +1,29 @@
+task checkstyleMain(type: Checkstyle) {
+    source 'src/main/java'
+    include '**/*.java'
+    classpath = files()
+    reports {
+        xml {
+            destination file("build/reports/checkstyle/main.xml")
+        }
+        html {
+            destination file("build/reports/checkstyle/main.html")
+        }
+    }
+    check.dependsOn it
+}
+
+task checkstyleTest(type: Checkstyle) {
+    source 'src/test/java'
+    include '**/*.java'
+    classpath = files()
+    reports {
+        xml {
+            destination file("build/reports/checkstyle/test.xml")
+        }
+        html {
+            destination file("build/reports/checkstyle/test.html")
+        }
+    }
+    check.dependsOn it
+}