BitmapWalker: do not revisit objects in bitmap

Currently, BitmapWalker walks through every object returned by the
internal ObjectWalk, regardless of whether that object has already
been marked in the bitmap. Set an object filter to ensure that only
bitmap-unmarked objects are walked through.

Change-Id: I22a8874b1e571df3c33643b365036d95f52fe7c7
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

org.eclipse.jgit/src/org/eclipse/jgit/revwalk/BitmapWalker.java

@@ -50,12 +50,14 @@ import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.revwalk.AddToBitmapFilter;
 import org.eclipse.jgit.internal.revwalk.AddUnseenToBitmapFilter;
+import org.eclipse.jgit.lib.AnyObjectId;
+import org.eclipse.jgit.lib.BitmapIndex;
 import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
 import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
-import org.eclipse.jgit.lib.BitmapIndex;
 import org.eclipse.jgit.lib.NullProgressMonitor;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ProgressMonitor;
+import org.eclipse.jgit.revwalk.filter.ObjectFilter;
 
 /**
  * Helper class to do ObjectWalks with pack index bitmaps.
@@ -200,6 +202,7 @@ public final class BitmapWalker {
 				walker.setRevFilter(
 						new AddUnseenToBitmapFilter(seen, bitmapResult));
 			}
+			walker.setObjectFilter(new BitmapObjectFilter(bitmapResult));
 
 			while (walker.next() != null) {
 				// Iterate through all of the commits. The BitmapRevFilter does
@@ -224,4 +227,22 @@ public final class BitmapWalker {
 
 		return bitmapResult;
 	}
+
+	/**
+	 * Filter that excludes objects already in the given bitmap.
+	 */
+	static class BitmapObjectFilter extends ObjectFilter {
+		private final BitmapBuilder bitmap;
+
+		BitmapObjectFilter(BitmapBuilder bitmap) {
+			this.bitmap = bitmap;
+		}
+
+		@Override
+		public final boolean include(ObjectWalk walker, AnyObjectId objid)
+			throws MissingObjectException, IncorrectObjectTypeException,
+			       IOException {
+			return !bitmap.contains(objid);
+		}
+	}
 }