Fix property name in gradle plugin documentation

See gh-25454

Author: jnizet

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-publish.gradle

@@ -21,3 +21,9 @@ bootBuildImage {
 	}
 }
 // end::publish[]
+
+task bootBuildImagePublish {
+    doFirst {
+        println(tasks.bootBuildImage.publish)
+    }
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/packaging/boot-build-image-publish.gradle.kts

@@ -13,7 +13,7 @@ tasks.getByName<BootJar>("bootJar") {
 // tag::publish[]
 tasks.getByName<BootBuildImage>("bootBuildImage") {
 	imageName = "docker.example.com/library/${project.name}"
-	publish = true
+	isPublish = true
 	docker {
 		publishRegistry {
 			username = "user"
@@ -24,3 +24,9 @@ tasks.getByName<BootBuildImage>("bootBuildImage") {
 	}
 }
 // end::publish[]
+
+tasks.register("bootBuildImagePublish") {
+    doFirst {
+        println(tasks.getByName<BootBuildImage>("bootBuildImage").isPublish)
+    }
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/test/java/org/springframework/boot/gradle/docs/PackagingDocumentationTests.java

@@ -242,6 +242,13 @@ void bootBuildImageWithCustomImageName() throws IOException {
 		assertThat(result.getOutput()).contains("example.com/library/" + this.gradleBuild.getProjectDir().getName());
 	}
 
+	@TestTemplate
+	void bootBuildImagePublish() throws IOException {
+		BuildResult result = this.gradleBuild.script("src/docs/gradle/packaging/boot-build-image-publish")
+				.build("bootBuildImagePublish");
+		assertThat(result.getOutput()).contains("true");
+	}
+
 	protected void jarFile(File file) throws IOException {
 		try (JarOutputStream jar = new JarOutputStream(new FileOutputStream(file))) {
 			jar.putNextEntry(new ZipEntry("META-INF/MANIFEST.MF"));