Use Instant instead of milliseconds for filesystem timestamp handling

This enables higher file timestamp resolution on filesystems like ext4,
Mac APFS (1ns) or NTFS (100ns) providing high timestamp resolution on
filesystem level.

Note:
- on some OSes Java 8,9 truncate milliseconds, see
https://bugs.openjdk.java.net/browse/JDK-8177809, fixed in Java 10
- UnixFileAttributes truncates timestamp resolution to microseconds when
converting the internal representation to FileTime exposed in the API,
see https://bugs.openjdk.java.net/browse/JDK-8181493
- WindowsFileAttributes also provides only microsecond resolution

Change-Id: I25ffff31a3c6f725fc345d4ddc2f26da3b88f6f2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowDirCache.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowDirCache.java
index 7f99d76bda..14a60a3b46 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowDirCache.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/ShowDirCache.java
@@ -48,8 +48,10 @@ package org.eclipse.jgit.pgm.debug;
 
 import static java.lang.Integer.valueOf;
 
-import java.text.SimpleDateFormat;
-import java.util.Date;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.Locale;
 
 import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.dircache.DirCacheEntry;
@@ -67,25 +69,27 @@ class ShowDirCache extends TextBuiltin {
 	/** {@inheritDoc} */
 	@Override
 	protected void run() throws Exception {
-		final SimpleDateFormat fmt;
-		fmt = new SimpleDateFormat("yyyy-MM-dd,HH:mm:ss.SSS"); //$NON-NLS-1$
+		final DateTimeFormatter fmt = DateTimeFormatter
+				.ofPattern("yyyy-MM-dd,HH:mm:ss.nnnnnnnnn") //$NON-NLS-1$
+				.withLocale(Locale.getDefault())
+				.withZone(ZoneId.systemDefault());
 
 		final DirCache cache = db.readDirCache();
 		for (int i = 0; i < cache.getEntryCount(); i++) {
 			final DirCacheEntry ent = cache.getEntry(i);
 			final FileMode mode = FileMode.fromBits(ent.getRawMode());
 			final int len = ent.getLength();
-			long lastModified = ent.getLastModified();
-			final Date mtime = new Date(lastModified);
+			Instant mtime = ent.getLastModifiedInstant();
 			final int stage = ent.getStage();
 
 			outw.print(mode);
 			outw.format(" %6d", valueOf(len)); //$NON-NLS-1$
 			outw.print(' ');
-			if (millis)
-				outw.print(lastModified);
-			else
+			if (millis) {
+				outw.print(mtime.toEpochMilli());
+			} else {
 				outw.print(fmt.format(mtime));
+			}
 			outw.print(' ');
 			outw.print(ent.getObjectId().name());
 			outw.print(' ');