Fix timestamp preservation when extracting cached files

The build cache extension was not properly preserving file and directory
timestamps when restoring attachedOutputs from cache. This caused Maven
to warn about files being 'more recent than the packaged artifact' even
after a successful build.

Root Causes:
1. The zip() method did not store directory entries with timestamps
2. The unzip() method set directory timestamps immediately, but they
   were later modified by Files.copy() operations for files within

Changes:
- Modified CacheUtils.zip() to store directory entries with timestamps
  via preVisitDirectory() callback
- Modified CacheUtils.unzip() to defer directory timestamp updates until
  after all files are extracted, preventing them from being overwritten
- Added Map<Path, Long> to track directory timestamps during extraction

This ensures that cached build outputs maintain their original timestamps,
preventing spurious warnings and improving build cache consistency.

Author: cowwoc

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

@@ -31,7 +31,9 @@
 import java.nio.file.attribute.FileTime;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
@@ -165,13 +167,26 @@ public static boolean zip(final Path dir, final Path zip, final String glob) thr
                     "*".equals(glob) ? null : FileSystems.getDefault().getPathMatcher("glob:" + glob);
             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() + "/";
+                        ZipEntry zipEntry = new ZipEntry(relativePath);
+                        zipEntry.setTime(attrs.lastModifiedTime().toMillis());
+                        zipOutputStream.putNextEntry(zipEntry);
+                        zipOutputStream.closeEntry();
+                    }
+                    return FileVisitResult.CONTINUE;
+                }
+
                 @Override
                 public FileVisitResult visitFile(Path path, BasicFileAttributes basicFileAttributes)
                         throws IOException {
 
                     if (matcher == null || matcher.matches(path.getFileName())) {
                         final ZipEntry zipEntry =
                                 new ZipEntry(dir.relativize(path).toString());
+                        zipEntry.setTime(basicFileAttributes.lastModifiedTime().toMillis());
                         zipOutputStream.putNextEntry(zipEntry);
                         Files.copy(path, zipOutputStream);
                         hasFiles.setTrue();
@@ -185,6 +200,7 @@ public FileVisitResult visitFile(Path path, BasicFileAttributes basicFileAttribu
     }
 
     public static void unzip(Path zip, Path out) throws IOException {
+        Map<Path, Long> directoryTimestamps = new HashMap<>();
         try (ZipInputStream zis = new ZipInputStream(Files.newInputStream(zip))) {
             ZipEntry entry = zis.getNextEntry();
             while (entry != null) {
@@ -193,16 +209,27 @@ public static void unzip(Path zip, Path out) throws IOException {
                     throw new RuntimeException("Bad zip entry");
                 }
                 if (entry.isDirectory()) {
-                    Files.createDirectory(file);
+                    if (!Files.exists(file)) {
+                        Files.createDirectories(file);
+                    }
+                    directoryTimestamps.put(file, entry.getTime());
                 } else {
                     Path parent = file.getParent();
-                    Files.createDirectories(parent);
+                    if (!Files.exists(parent)) {
+                        Files.createDirectories(parent);
+                    }
                     Files.copy(zis, file, StandardCopyOption.REPLACE_EXISTING);
+                    Files.setLastModifiedTime(file, FileTime.fromMillis(entry.getTime()));
                 }
-                Files.setLastModifiedTime(file, FileTime.fromMillis(entry.getTime()));
                 entry = zis.getNextEntry();
             }
         }
+
+        // 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()));
+        }
     }
 
     public static <T> void debugPrintCollection(