Lazily initialize GitRatchetGradle to avoid loading JGit at configuration time

GitRatchetGradle is instantiated eagerly when SpotlessTaskService is
created, which happens during Gradle configuration. Its static
initializer installs a custom JGit SystemReader that reads
~/.gitconfig. This causes Gradle's configuration cache to fingerprint
the file even when no Spotless tasks are requested.

Defer instantiation to getRatchet(), which is only called during task
execution. This avoids loading JGit classes and reading git config
files at configuration time.

Author: joshfriend

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskService.java

@@ -99,9 +99,12 @@ void registerApplyAlreadyRan(SpotlessApply task) {
 	}
 
 	// <GitRatchet>
-	private final GitRatchetGradle ratchet = new GitRatchetGradle();
+	private GitRatchetGradle ratchet;
 
 	GitRatchetGradle getRatchet() {
+		if (ratchet == null) {
+			ratchet = new GitRatchetGradle();
+		}
 		return ratchet;
 	}
 
@@ -112,7 +115,9 @@ public void onFinish(FinishEvent var1) {
 
 	@Override
 	public void close() throws Exception {
-		ratchet.close();
+		if (ratchet != null) {
+			ratchet.close();
+		}
 	}
 	// </GitRatchet>
 

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/ConfigurationCacheTest.java

@@ -15,8 +15,12 @@
  */
 package com.diffplug.gradle.spotless;
 
+import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 
+import org.assertj.core.api.Assertions;
 import org.gradle.testkit.runner.GradleRunner;
 import org.junit.jupiter.api.Test;
 
@@ -60,6 +64,52 @@ public void helpConfiguresIfTasksAreCreated() throws IOException {
 		gradleRunner().withArguments("help").build();
 	}
 
+	@Test
+	public void configurationCacheNotInvalidatedByGitconfig() throws IOException {
+		// ~/.gitconfig is read by JGit at class-load time via the SystemReader.
+		// If GitRatchetGradle is loaded eagerly during configuration, Gradle's
+		// configuration cache fingerprints ~/.gitconfig. When its content changes
+		// (e.g. CI workers inject per-build auth tokens), the cache is invalidated.
+		// This test verifies that changing ~/.gitconfig between runs does not
+		// invalidate the configuration cache.
+		Path gitconfig = Path.of(System.getProperty("user.home"), ".gitconfig");
+		boolean existed = Files.exists(gitconfig);
+		String originalContent = existed ? Files.readString(gitconfig) : null;
+		try {
+			Files.writeString(gitconfig, "[user]\n\tname = test\n");
+
+			setFile("build.gradle").toLines(
+					"plugins {",
+					"    id 'com.diffplug.spotless'",
+					"}",
+					"repositories { mavenCentral() }",
+					"apply plugin: 'java'",
+					"spotless {",
+					"    java {",
+					"        googleJavaFormat()",
+					"    }",
+					"}");
+			setFile("src/main/java/test.java").toResource("java/googlejavaformat/JavaCodeUnformatted.test");
+
+			// first run stores the configuration cache
+			gradleRunner().withArguments("help").build();
+
+			// change ~/.gitconfig content between runs
+			Files.writeString(gitconfig, "[user]\n\tname = test\n[http]\n\textraheader = changed\n");
+
+			// second run must reuse the configuration cache despite the change
+			String output = gradleRunner().withArguments("help").build().getOutput();
+			Assertions.assertThat(output).contains("Reusing configuration cache.");
+		} finally {
+			// restore original ~/.gitconfig
+			if (originalContent != null) {
+				Files.writeString(gitconfig, originalContent);
+			} else if (Files.exists(gitconfig)) {
+				Files.delete(gitconfig);
+			}
+		}
+	}
+
 	@Test
 	public void multipleRuns() throws IOException {
 		setFile("build.gradle").toLines(