Introduce ObjectLoader.Filter for delegation

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: I78ada3f4023c4304b19f94fb044024f0f0b2cbbe

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

@@ -323,4 +323,42 @@ public abstract class ObjectLoader {
 			return new ObjectStream.SmallStream(this);
 		}
 	}
+
+	/**
+	 * Wraps a delegate ObjectLoader.
+	 *
+	 * @since 4.10
+	 */
+	public static abstract class Filter extends ObjectLoader {
+		/**
+		 * @return delegate ObjectLoader to handle all processing.
+		 * @since 4.10
+		 */
+		protected abstract ObjectLoader delegate();
+
+		@Override
+		public int getType() {
+			return delegate().getType();
+		}
+
+		@Override
+		public long getSize() {
+			return delegate().getSize();
+		}
+
+		@Override
+		public boolean isLarge() {
+			return delegate().isLarge();
+		}
+
+		@Override
+		public byte[] getCachedBytes() {
+			return delegate().getCachedBytes();
+		}
+
+		@Override
+		public ObjectStream openStream() throws IOException {
+			return delegate().openStream();
+		}
+	}
 }