Reset ObjectWalker when it starts a new walk

The ObjectWalker in PackWriterBitmapWalker needs to be reset whenever it
starts a new walk. Move this responsibility from the caller to the
method when the new walk starts.

Change-Id: Ib66003be1b5bdc80f46b9bbbb17d45e616714912
Signed-off-by: Zhen Chen <czhen@google.com>

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

 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
 		BitmapBuilder haveBitmap = bitmapWalker.findObjects(have, null, true);
-		bitmapWalker.reset();
 		BitmapBuilder wantBitmap = bitmapWalker.findObjects(want, haveBitmap,
 				false);
 		BitmapBuilder needBitmap = wantBitmap.andNot(haveBitmap);
 		PackWriterBitmapWalker walker = bitmapPreparer.newBitmapWalker();
 		AnyObjectId last = null;
 		for (PackWriterBitmapPreparer.BitmapCommit cmit : selectedCommits) {
-			if (cmit.isReuseWalker())
-				walker.reset();
-			else
+			if (!cmit.isReuseWalker()) {
 				walker = bitmapPreparer.newBitmapWalker();
-
+			}
 			BitmapBuilder bitmap = walker.findObjects(
 					Collections.singleton(cmit), null, false);
 

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

 		return countOfBitmapIndexMisses;
 	}
 
-	BitmapBuilder findObjects(Iterable<? extends ObjectId> start, BitmapBuilder seen, boolean ignoreMissing)
+	BitmapBuilder findObjects(Iterable<? extends ObjectId> start, BitmapBuilder seen,
+			boolean ignoreMissing)
 			throws MissingObjectException, IncorrectObjectTypeException,
 				   IOException {
 		if (!ignoreMissing) {
 		return result;
 	}
 
-	private BitmapBuilder findObjectsWalk(Iterable<? extends ObjectId> start, BitmapBuilder seen, boolean ignoreMissingStart)
+	private BitmapBuilder findObjectsWalk(Iterable<? extends ObjectId> start, BitmapBuilder seen,
+			boolean ignoreMissingStart)
 			throws MissingObjectException, IncorrectObjectTypeException,
 			IOException {
+		walker.reset();
 		final BitmapBuilder bitmapResult = bitmapIndex.newBitmapBuilder();
 
 		for (ObjectId obj : start) {
 		return bitmapResult;
 	}
 
-	void reset() {
-		walker.reset();
-	}
-
 	/**
 	 * A RevFilter that adds the visited commits to {@code bitmap} as a side
 	 * effect.