KT-18765 Move incremental compilation message from Gradle's warning to info logging level

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseGradleIT.kt

@@ -418,7 +418,16 @@ abstract class BaseGradleIT {
     private fun Project.createGradleTailParameters(options: BuildOptions, params: Array<out String> = arrayOf()): List<String> =
             params.toMutableList().apply {
                 add("--stacktrace")
-                add("--${minLogLevel.name.toLowerCase()}")
+                when (minLogLevel) {
+                    // Do not allow to configure Gradle project with `ERROR` log level (error logs visible on all log levels)
+                    LogLevel.ERROR -> error("Log level ERROR is not supported by Gradle command-line")
+                    // Omit log level argument for default `LIFECYCLE` log level,
+                    // because there is no such command-line option `--lifecycle`
+                    // see https://docs.gradle.org/current/userguide/logging.html#sec:choosing_a_log_level
+                    LogLevel.LIFECYCLE -> Unit
+                    //Command line option for other log levels
+                    else -> add("--${minLogLevel.name.toLowerCase()}")
+                }
                 if (options.daemonOptionSupported) {
                     add(if (options.withDaemon) "--daemon" else "--no-daemon")
                 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginIT.kt

@@ -265,6 +265,19 @@ class KotlinGradleIT: BaseGradleIT() {
         }
     }
 
+    @Test
+    fun testIncrementalCompilationLogLevel() {
+        val infoProject = Project("kotlinProject", GRADLE_VERSION, minLogLevel = LogLevel.INFO)
+        infoProject.build("build") {
+            assertContains(USING_INCREMENTAL_COMPILATION_MESSAGE)
+        }
+
+        val lifecycleProject = Project("kotlinProject", GRADLE_VERSION, minLogLevel = LogLevel.LIFECYCLE)
+        lifecycleProject.build("build") {
+            assertNotContains(USING_INCREMENTAL_COMPILATION_MESSAGE)
+        }
+    }
+
     @Test
     fun testConvertJavaToKotlin() {
         val project = Project("convertBetweenJavaAndKotlin", GRADLE_VERSION)

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -315,7 +315,7 @@ open class KotlinCompile : AbstractKotlinCompile<K2JVMCompilerArguments>(), Kotl
         val environment = when {
             !incremental -> GradleCompilerEnvironment(computedCompilerClasspath, messageCollector, outputItemCollector, args)
             else -> {
-                logger.warn(USING_INCREMENTAL_COMPILATION_MESSAGE)
+                logger.info(USING_INCREMENTAL_COMPILATION_MESSAGE)
                 GradleIncrementalCompilerEnvironment(computedCompilerClasspath, changedFiles, reporter, taskBuildDirectory,
                         messageCollector, outputItemCollector, args, kaptAnnotationsFileUpdater,
                         artifactDifferenceRegistryProvider,