Use the ObjectStream size during copyTo

If the stream is a delta decompression stream, getting the size
can be expensive.  Its cheaper to get it from the stream itself
rather than from the object loader.

Change-Id: Ia7f0af98681f6d56ea419a48c6fa8eea09274b28
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectLoader.java

@@ -166,6 +166,7 @@ public abstract class ObjectLoader {
 		if (isLarge()) {
 			ObjectStream in = openStream();
 			try {
+				final long sz = in.getSize();
 				byte[] tmp = new byte[1024];
 				long copied = 0;
 				for (;;) {
@@ -175,7 +176,7 @@ public abstract class ObjectLoader {
 					out.write(tmp, 0, n);
 					copied += n;
 				}
-				if (copied != getSize())
+				if (copied != sz)
 					throw new EOFException();
 			} finally {
 				in.close();