Handle long file names in buildpack images

Fixes gh-26445

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/main/java/org/springframework/boot/buildpack/platform/build/ImageBuildpack.java

@@ -124,6 +124,7 @@ final class ImageBuildpack implements Buildpack {
 		private void copyLayerTar(Path path, OutputStream out) throws IOException {
 			try (TarArchiveInputStream tarIn = new TarArchiveInputStream(Files.newInputStream(path));
 					TarArchiveOutputStream tarOut = new TarArchiveOutputStream(out)) {
+				tarOut.setLongFileMode(TarArchiveOutputStream.LONGFILE_POSIX);
 				TarArchiveEntry entry = tarIn.getNextTarEntry();
 				while (entry != null) {
 					if (entry.isFile()) {

spring-boot-project/spring-boot-tools/spring-boot-buildpack-platform/src/test/java/org/springframework/boot/buildpack/platform/build/ImageBuildpackTests.java

@@ -21,9 +21,12 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Random;
 
 import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
 import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;
+import org.apache.commons.compress.archivers.tar.TarArchiveOutputStream;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.mockito.invocation.InvocationOnMock;
 
@@ -31,10 +34,10 @@ import org.springframework.boot.buildpack.platform.docker.type.Image;
 import org.springframework.boot.buildpack.platform.io.IOBiConsumer;
 import org.springframework.boot.buildpack.platform.io.TarArchive;
 import org.springframework.boot.buildpack.platform.json.AbstractJsonTests;
-import org.springframework.util.FileCopyUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.fail;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.BDDMockito.willAnswer;
@@ -48,6 +51,15 @@ import static org.mockito.Mockito.mock;
  */
 class ImageBuildpackTests extends AbstractJsonTests {
 
+	private String longFilePath;
+
+	@BeforeEach
+	void setUp() {
+		StringBuilder path = new StringBuilder();
+		new Random().ints('a', 'z' + 1).limit(100).forEach((i) -> path.append((char) i));
+		this.longFilePath = path.toString();
+	}
+
 	@Test
 	void resolveWhenFullyQualifiedReferenceReturnsBuilder() throws Exception {
 		Image image = Image.of(getContent("buildpack-image.json"));
@@ -108,13 +120,31 @@ class ImageBuildpackTests extends AbstractJsonTests {
 		assertThat(buildpack).isNull();
 	}
 
-	private Object withMockLayers(InvocationOnMock invocation) throws Exception {
-		IOBiConsumer<String, TarArchive> consumer = invocation.getArgument(1);
-		TarArchive archive = (out) -> FileCopyUtils.copy(getClass().getResourceAsStream("layer.tar"), out);
-		consumer.accept("test", archive);
+	private Object withMockLayers(InvocationOnMock invocation) {
+		try {
+			IOBiConsumer<String, TarArchive> consumer = invocation.getArgument(1);
+			TarArchive archive = (out) -> {
+				try (TarArchiveOutputStream tarOut = new TarArchiveOutputStream(out)) {
+					tarOut.setLongFileMode(TarArchiveOutputStream.LONGFILE_POSIX);
+					writeTarEntry(tarOut, "/cnb/buildpacks/example_buildpack/0.0.1/buildpack.toml");
+					writeTarEntry(tarOut, "/cnb/buildpacks/example_buildpack/0.0.1/" + this.longFilePath);
+					tarOut.finish();
+				}
+			};
+			consumer.accept("test", archive);
+		}
+		catch (IOException ex) {
+			fail("Error writing mock layers", ex);
+		}
 		return null;
 	}
 
+	private void writeTarEntry(TarArchiveOutputStream tarOut, String name) throws IOException {
+		TarArchiveEntry entry = new TarArchiveEntry(name);
+		tarOut.putArchiveEntry(entry);
+		tarOut.closeArchiveEntry();
+	}
+
 	private void assertHasExpectedLayers(Buildpack buildpack) throws IOException {
 		List<ByteArrayOutputStream> layers = new ArrayList<>();
 		buildpack.apply((layer) -> {
@@ -132,7 +162,8 @@ class ImageBuildpackTests extends AbstractJsonTests {
 				entry = tar.getNextTarEntry();
 			}
 		}
-		assertThat(names).containsExactly("etc/apt/sources.list");
+		assertThat(names).containsExactlyInAnyOrder("cnb/buildpacks/example_buildpack/0.0.1/buildpack.toml",
+				"cnb/buildpacks/example_buildpack/0.0.1/" + this.longFilePath);
 	}
 
 }