PackWriter/Statistics: Report offloaded size

Add to statistics the amount and size of packfiles offloaded to HTTP
download.

Change-Id: I895a7219ecac2794368bfc4fdfae74c1238deed9
Signed-off-by: Ivan Frade <ifrade@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/PackWriter.java

@@ -1230,6 +1230,8 @@ public class PackWriter implements AutoCloseable {
 					if (packInfo != null) {
 						o.writeString(packInfo.getHash() + ' ' +
 								packInfo.getUri() + '\n');
+						stats.offloadedPackfiles += 1;
+						stats.offloadedPackfileSize += packInfo.getSize();
 					} else {
 						unwrittenCachedPacks.add(pack);
 					}

org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackStatistics.java

@@ -270,6 +270,20 @@ public class PackStatistics {
 		 * @since 5.4*/
 		public long treesTraversed;
 
+		/**
+		 * Amount of packfile uris sent to the client to download via HTTP.
+		 *
+		 * @since 5.6
+		 */
+		public long offloadedPackfiles;
+
+		/**
+		 * Total size (in bytes) offloaded to HTTP downloads.
+		 *
+		 * @since 5.6
+		 */
+		public long offloadedPackfileSize;
+
 		/**
 		 * Statistics about each object type in the pack (commits, tags, trees
 		 * and blobs.)
@@ -597,6 +611,22 @@ public class PackStatistics {
 		return statistics.treesTraversed;
 	}
 
+	/**
+	 * @return amount of packfiles offloaded (sent as "packfile-uri")/
+	 * @since 5.6
+	 */
+	public long getOffloadedPackfiles() {
+		return statistics.offloadedPackfiles;
+	}
+
+	/**
+	 * @return total size (in bytes) offloaded to HTTP downloads.
+	 * @since 5.6
+	 */
+	public long getOffloadedPackfilesSize() {
+		return statistics.offloadedPackfileSize;
+	}
+
 	/**
 	 * Get total time spent processing this pack.
 	 *