Simplfy caching of DfsPackDescription from PackWriter.Statistics

Let the pack description copy the relevant stats values. This
moves it out of the garbage collector and compactor algorithms,
co-locating with something that might care.

Remove some unnecessary code from the DfsPackCompactor, the stats
tracks the same information and can supply it.

Change-Id: Id64ab38d507c0ed19ae0d106862d175b7364eba3

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsGarbageCollector.java

@@ -403,9 +403,6 @@ public class DfsGarbageCollector {
 
 		PackWriter.Statistics stats = pw.getStatistics();
 		pack.setPackStats(stats);
-		pack.setFileSize(PACK, stats.getTotalBytes());
-		pack.setObjectCount(stats.getTotalObjects());
-		pack.setDeltaCount(stats.getTotalDeltas());
 		objectsPacked += stats.getTotalObjects();
 		newPackStats.add(stats);
 

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsPackCompactor.java

@@ -283,20 +283,19 @@ public class DfsPackCompactor {
 		pm.endTask();
 	}
 
-	private void writePack(DfsObjDatabase objdb, DfsPackDescription pack,
+	private static void writePack(DfsObjDatabase objdb,
+			DfsPackDescription pack,
 			PackWriter pw, ProgressMonitor pm) throws IOException {
 		DfsOutputStream out = objdb.writeFile(pack, PACK);
 		try {
-			CountingOutputStream cnt = new CountingOutputStream(out);
-			pw.writePack(pm, pm, cnt);
-			pack.setObjectCount(pw.getObjectCount());
-			pack.setFileSize(PACK, cnt.getCount());
+			pw.writePack(pm, pm, out);
 		} finally {
 			out.close();
 		}
 	}
 
-	private void writeIndex(DfsObjDatabase objdb, DfsPackDescription pack,
+	private static void writeIndex(DfsObjDatabase objdb,
+			DfsPackDescription pack,
 			PackWriter pw) throws IOException {
 		DfsOutputStream out = objdb.writeFile(pack, INDEX);
 		try {

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsPackDescription.java

@@ -43,6 +43,8 @@
 
 package org.eclipse.jgit.storage.dfs;
 
+import static org.eclipse.jgit.storage.pack.PackExt.PACK;
+
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
@@ -248,6 +250,9 @@ public class DfsPackDescription implements Comparable<DfsPackDescription> {
 
 	DfsPackDescription setPackStats(PackWriter.Statistics stats) {
 		this.stats = stats;
+		setFileSize(PACK, stats.getTotalBytes());
+		setObjectCount(stats.getTotalObjects());
+		setDeltaCount(stats.getTotalDeltas());
 		return this;
 	}