Add ObjectReader.Filter, like in ObjectInserter

Change-Id: If34ad8185dc8192435e622995fdca598b86add7e

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

@@ -431,4 +431,102 @@ public abstract class ObjectReader implements AutoCloseable {
 	 */
 	@Override
 	public abstract void close();
+
+	/**
+	 * Wraps a delegate ObjectReader.
+	 *
+	 * @since 4.4
+	 */
+	public static abstract class Filter extends ObjectReader {
+		/**
+		 * @return delegate ObjectReader to handle all processing.
+		 * @since 4.4
+		 */
+		protected abstract ObjectReader delegate();
+
+		@Override
+		public ObjectReader newReader() {
+			return delegate().newReader();
+		}
+
+		@Override
+		public AbbreviatedObjectId abbreviate(AnyObjectId objectId)
+				throws IOException {
+			return delegate().abbreviate(objectId);
+		}
+
+		@Override
+		public AbbreviatedObjectId abbreviate(AnyObjectId objectId, int len)
+				throws IOException {
+			return delegate().abbreviate(objectId, len);
+		}
+
+		@Override
+		public Collection<ObjectId> resolve(AbbreviatedObjectId id)
+				throws IOException {
+			return delegate().resolve(id);
+		}
+
+		@Override
+		public boolean has(AnyObjectId objectId) throws IOException {
+			return delegate().has(objectId);
+		}
+
+		@Override
+		public boolean has(AnyObjectId objectId, int typeHint) throws IOException {
+			return delegate().has(objectId, typeHint);
+		}
+
+		@Override
+		public ObjectLoader open(AnyObjectId objectId)
+				throws MissingObjectException, IOException {
+			return delegate().open(objectId);
+		}
+
+		@Override
+		public ObjectLoader open(AnyObjectId objectId, int typeHint)
+				throws MissingObjectException, IncorrectObjectTypeException,
+				IOException {
+			return delegate().open(objectId, typeHint);
+		}
+
+		@Override
+		public Set<ObjectId> getShallowCommits() throws IOException {
+			return delegate().getShallowCommits();
+		}
+
+		@Override
+		public <T extends ObjectId> AsyncObjectLoaderQueue<T> open(
+				Iterable<T> objectIds, boolean reportMissing) {
+			return delegate().open(objectIds, reportMissing);
+		}
+
+		@Override
+		public long getObjectSize(AnyObjectId objectId, int typeHint)
+				throws MissingObjectException, IncorrectObjectTypeException,
+				IOException {
+			return delegate().getObjectSize(objectId, typeHint);
+		}
+
+		@Override
+		public <T extends ObjectId> AsyncObjectSizeQueue<T> getObjectSize(
+				Iterable<T> objectIds, boolean reportMissing) {
+			return delegate().getObjectSize(objectIds, reportMissing);
+		}
+
+		@Override
+		public void setAvoidUnreachableObjects(boolean avoid) {
+			delegate().setAvoidUnreachableObjects(avoid);
+		}
+
+		@Override
+		public BitmapIndex getBitmapIndex() throws IOException {
+			return delegate().getBitmapIndex();
+		}
+
+		@Override
+		public void close() {
+			delegate().close();
+		}
+	}
 }