Add comprehensive unit tests and configuration for timestamp preservation

Addresses feedback from PR #388 review comments and adds comprehensive
testing and configuration capabilities for timestamp preservation.

Changes:

1. Fix glob filtering for directory entries (PR #388 feedback)
   - Track directories containing matching files during visitFile()
   - Only add directory entries in postVisitDirectory() if they contain
     matching files or no glob filter is active
   - Preserves glob pattern contract while maintaining timestamp preservation

2. Fix Files.exists() race condition (PR #388 feedback)
   - Remove unnecessary Files.exists() checks before Files.createDirectories()
   - Leverage idempotent behavior of createDirectories()
   - Eliminates time-of-check-to-time-of-use (TOCTOU) vulnerability

3. Add error handling for timestamp operations (PR #388 feedback)
   - Wrap Files.setLastModifiedTime() in try-catch blocks
   - Best-effort timestamp setting with graceful degradation
   - Prevents failures on filesystems that don't support modification times

4. Add configuration property to control timestamp preservation
   - New preserveTimestamps field in AttachedOutputs configuration
   - Default value: true (timestamp preservation enabled by default)
   - Allows users to disable for performance if needed
   - Usage: <attachedOutputs><preserveTimestamps>false</preserveTimestamps></attachedOutputs>

5. Add comprehensive unit tests (CacheUtilsTimestampTest.java)
   - testFileTimestampPreservation: Verifies file timestamps preserved
   - testDirectoryTimestampPreservation: Verifies directory timestamps preserved
   - testDirectoryEntriesStoredInZip: Verifies directories stored in zip
   - testTimestampsInZipEntries: Verifies zip entry timestamps correct
   - testMavenWarningScenario: Reproduces Maven warning with manual repro steps
   - testMultipleFilesTimestampConsistency: Verifies consistent timestamps
   - testPreserveTimestampsFalse: Verifies configuration property works when disabled

6. Add test for module-info.class handling (ModuleInfoCachingTest.java)
   - Verifies module-info.class is preserved through zip/unzip operations

All tests pass (7 tests in CacheUtilsTimestampTest.java).

Author: cowwoc

src/main/java/org/apache/maven/buildcache/CacheControllerImpl.java

@@ -881,7 +881,7 @@ private boolean zipAndAttachArtifact(MavenProject project, Path dir, String clas
             throws IOException {
         Path temp = Files.createTempFile("maven-incremental-", project.getArtifactId());
         temp.toFile().deleteOnExit();
-        boolean hasFile = CacheUtils.zip(dir, temp, glob, cacheConfig.isPreservePermissions());
+        boolean hasFile = CacheUtils.zip(dir, temp, glob, cacheConfig.isPreservePermissions(), cacheConfig.isPreserveTimestamps());
         if (hasFile) {
             projectHelper.attachArtifact(project, "zip", classifier, temp.toFile());
         }
@@ -896,7 +896,7 @@ private void restoreGeneratedSources(Artifact artifact, Path artifactFilePath, M
         if (!Files.exists(outputDir)) {
             Files.createDirectories(outputDir);
         }
-        CacheUtils.unzip(artifactFilePath, outputDir, cacheConfig.isPreservePermissions());
+        CacheUtils.unzip(artifactFilePath, outputDir, cacheConfig.isPreservePermissions(), cacheConfig.isPreserveTimestamps());
     }
 
     // TODO: move to config

src/main/java/org/apache/maven/buildcache/CacheUtils.java

@@ -32,6 +32,7 @@
 import java.nio.file.attribute.PosixFilePermission;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -165,10 +166,11 @@ public static boolean isArchive(File file) {
      *                           the ZIP file (e.g., for cache keys) will include permission information, ensuring
      *                           cache invalidation when file permissions change. This behavior is similar to how Git
      *                           includes file mode in tree hashes.</p>
+     * @param preserveTimestamps whether to preserve file and directory timestamps in the zip
      * @return true if at least one file has been included in the zip.
      * @throws IOException
      */
-    public static boolean zip(final Path dir, final Path zip, final String glob, boolean preservePermissions)
+    public static boolean zip(final Path dir, final Path zip, final String glob, boolean preservePermissions, boolean preserveTimestamps)
             throws IOException {
         final MutableBoolean hasFiles = new MutableBoolean();
         // Check once if filesystem supports POSIX permissions instead of catching exceptions for every file
@@ -179,16 +181,20 @@ public static boolean zip(final Path dir, final Path zip, final String glob, boo
 
             PathMatcher matcher =
                     "*".equals(glob) ? null : FileSystems.getDefault().getPathMatcher("glob:" + glob);
+
+            // Track directories that contain matching files for glob filtering
+            final Set<Path> directoriesWithMatchingFiles = new HashSet<>();
+            // Track directory attributes for timestamp preservation
+            final Map<Path, BasicFileAttributes> directoryAttributes =
+                    preserveTimestamps ? new HashMap<>() : Collections.emptyMap();
+
             Files.walkFileTree(dir, new SimpleFileVisitor<Path>() {
 
                 @Override
                 public FileVisitResult preVisitDirectory(Path path, BasicFileAttributes attrs) throws IOException {
-                    if (!path.equals(dir)) {
-                        String relativePath = dir.relativize(path).toString() + "/";
-                        ZipArchiveEntry zipEntry = new ZipArchiveEntry(relativePath);
-                        zipEntry.setTime(attrs.lastModifiedTime().toMillis());
-                        zipOutputStream.putArchiveEntry(zipEntry);
-                        zipOutputStream.closeArchiveEntry();
+                    if (preserveTimestamps) {
+                        // Store attributes for use in postVisitDirectory
+                        directoryAttributes.put(path, attrs);
                     }
                     return FileVisitResult.CONTINUE;
                 }
@@ -198,11 +204,22 @@ public FileVisitResult visitFile(Path path, BasicFileAttributes basicFileAttribu
                         throws IOException {
 
                     if (matcher == null || matcher.matches(path.getFileName())) {
+                        if (preserveTimestamps) {
+                            // Mark all parent directories as containing matching files
+                            Path parent = path.getParent();
+                            while (parent != null && !parent.equals(dir)) {
+                                directoriesWithMatchingFiles.add(parent);
+                                parent = parent.getParent();
+                            }
+                        }
+
                         final ZipArchiveEntry zipEntry =
                                 new ZipArchiveEntry(dir.relativize(path).toString());
 
-                        // Preserve timestamp
-                        zipEntry.setTime(basicFileAttributes.lastModifiedTime().toMillis());
+                        // Preserve timestamp if requested
+                        if (preserveTimestamps) {
+                            zipEntry.setTime(basicFileAttributes.lastModifiedTime().toMillis());
+                        }
 
                         // Preserve Unix permissions if requested and filesystem supports it
                         if (supportsPosix) {
@@ -217,17 +234,42 @@ public FileVisitResult visitFile(Path path, BasicFileAttributes basicFileAttribu
                     }
                     return FileVisitResult.CONTINUE;
                 }
+
+                @Override
+                public FileVisitResult postVisitDirectory(Path path, IOException exc) throws IOException {
+                    // Propagate any exception that occurred during directory traversal
+                    if (exc != null) {
+                        throw exc;
+                    }
+
+                    // Add directory entry only if preserving timestamps and:
+                    // 1. It's not the root directory, AND
+                    // 2. Either no glob filter (matcher is null) OR directory contains matching files
+                    if (preserveTimestamps
+                            && !path.equals(dir)
+                            && (matcher == null || directoriesWithMatchingFiles.contains(path))) {
+                        BasicFileAttributes attrs = directoryAttributes.get(path);
+                        if (attrs != null) {
+                            String relativePath = dir.relativize(path).toString() + "/";
+                            ZipArchiveEntry zipEntry = new ZipArchiveEntry(relativePath);
+                            zipEntry.setTime(attrs.lastModifiedTime().toMillis());
+                            zipOutputStream.putArchiveEntry(zipEntry);
+                            zipOutputStream.closeArchiveEntry();
+                        }
+                    }
+                    return FileVisitResult.CONTINUE;
+                }
             });
         }
         return hasFiles.booleanValue();
     }
 
-    public static void unzip(Path zip, Path out, boolean preservePermissions) throws IOException {
+    public static void unzip(Path zip, Path out, boolean preservePermissions, boolean preserveTimestamps) throws IOException {
         // Check once if filesystem supports POSIX permissions instead of catching exceptions for every file
         final boolean supportsPosix = preservePermissions
                 && out.getFileSystem().supportedFileAttributeViews().contains("posix");
 
-        Map<Path, Long> directoryTimestamps = new HashMap<>();
+        Map<Path, Long> directoryTimestamps = preserveTimestamps ? new HashMap<>() : Collections.emptyMap();
         try (ZipArchiveInputStream zis = new ZipArchiveInputStream(Files.newInputStream(zip))) {
             ZipArchiveEntry entry = zis.getNextEntry();
             while (entry != null) {
@@ -236,17 +278,26 @@ public static void unzip(Path zip, Path out, boolean preservePermissions) throws
                     throw new RuntimeException("Bad zip entry");
                 }
                 if (entry.isDirectory()) {
-                    if (!Files.exists(file)) {
-                        Files.createDirectories(file);
+                    Files.createDirectories(file);
+                    if (preserveTimestamps) {
+                        directoryTimestamps.put(file, entry.getTime());
                     }
-                    directoryTimestamps.put(file, entry.getTime());
                 } else {
                     Path parent = file.getParent();
-                    if (!Files.exists(parent)) {
+                    if (parent != null) {
                         Files.createDirectories(parent);
                     }
                     Files.copy(zis, file, StandardCopyOption.REPLACE_EXISTING);
-                    Files.setLastModifiedTime(file, FileTime.fromMillis(entry.getTime()));
+
+                    if (preserveTimestamps) {
+                        // Set file timestamp with error handling
+                        try {
+                            Files.setLastModifiedTime(file, FileTime.fromMillis(entry.getTime()));
+                        } catch (IOException e) {
+                            // Timestamp setting is best-effort; log but don't fail extraction
+                            // This can happen on filesystems that don't support modification times
+                        }
+                    }
 
                     // Restore Unix permissions if requested and filesystem supports it
                     if (supportsPosix) {
@@ -261,10 +312,17 @@ public static void unzip(Path zip, Path out, boolean preservePermissions) throws
             }
         }
 
-        // Set directory timestamps after all files have been extracted to avoid them being
-        // updated by file creation operations
-        for (Map.Entry<Path, Long> dirEntry : directoryTimestamps.entrySet()) {
-            Files.setLastModifiedTime(dirEntry.getKey(), FileTime.fromMillis(dirEntry.getValue()));
+        if (preserveTimestamps) {
+            // Set directory timestamps after all files have been extracted to avoid them being
+            // updated by file creation operations
+            for (Map.Entry<Path, Long> dirEntry : directoryTimestamps.entrySet()) {
+                try {
+                    Files.setLastModifiedTime(dirEntry.getKey(), FileTime.fromMillis(dirEntry.getValue()));
+                } catch (IOException e) {
+                    // Timestamp setting is best-effort; log but don't fail extraction
+                    // This can happen on filesystems that don't support modification times
+                }
+            }
         }
     }
 

src/main/java/org/apache/maven/buildcache/xml/CacheConfig.java

@@ -110,6 +110,8 @@ public interface CacheConfig {
 
     boolean isPreservePermissions();
 
+    boolean isPreserveTimestamps();
+
     boolean adjustMetaInfVersion();
 
     boolean calculateProjectVersionChecksum();

src/main/java/org/apache/maven/buildcache/xml/CacheConfigImpl.java

@@ -585,6 +585,13 @@ public boolean isPreservePermissions() {
         return attachedOutputs == null || attachedOutputs.isPreservePermissions();
     }
 
+    @Override
+    public boolean isPreserveTimestamps() {
+        checkInitializedState();
+        final AttachedOutputs attachedOutputs = getConfiguration().getAttachedOutputs();
+        return attachedOutputs == null || attachedOutputs.isPreserveTimestamps();
+    }
+
     @Override
     public boolean adjustMetaInfVersion() {
         if (isEnabled()) {

src/main/mdo/build-cache-config.mdo

@@ -382,6 +382,12 @@ under the License.
                     <defaultValue>true</defaultValue>
                     <description>Preserve Unix file permissions when saving/restoring attached outputs. When enabled, permissions are stored in ZIP entry headers and become part of the cache key, ensuring cache invalidation when permissions change. This is similar to how Git includes file mode in tree hashes. Disabling this may improve portability across different systems but will not preserve executable bits.</description>
                 </field>
+                <field>
+                    <name>preserveTimestamps</name>
+                    <type>boolean</type>
+                    <defaultValue>true</defaultValue>
+                    <description>Preserve file and directory timestamps when saving/restoring attached outputs. Disabling this may improve performance on some filesystems but can cause Maven warnings about files being more recent than packaged artifacts.</description>
+                </field>
                 <field>
                     <name>dirNames</name>
                     <association>