In LockFile#waitForStatChange wait in units of file time resolution

Since we now measure file time resolution we can use it to replace the
hard coded wait time of 25ms. FileSnapshot#equals will return true until
the mtime of the old (o) and the new FileSnapshot (n) differ by at least
one  file time resolution.

Change-Id: Icb713a80ce9eb929242ed083406bfb6650c72223
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java

@@ -61,6 +61,7 @@ import java.nio.file.StandardCopyOption;
 import java.nio.file.attribute.FileTime;
 import java.text.MessageFormat;
 import java.time.Instant;
+import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.lib.Constants;
@@ -425,8 +426,10 @@ public class LockFile {
 	public void waitForStatChange() throws InterruptedException {
 		FileSnapshot o = FileSnapshot.save(ref);
 		FileSnapshot n = FileSnapshot.save(lck);
+		long fsTimeResolution = FS.getFileStoreAttributes(lck.toPath())
+				.getFsTimestampResolution().toNanos();
 		while (o.equals(n)) {
-			Thread.sleep(25 /* milliseconds */);
+			TimeUnit.NANOSECONDS.sleep(fsTimeResolution);
 			try {
 				Files.setLastModifiedTime(lck.toPath(),
 						FileTime.from(Instant.now()));