Replace anonymous BitmapRevFilter subclasses with explicit classes

This puts the code for include() in each RevFilter returned by
newRevFilter in one place and should make the code easier to
understand and modify.

Change-Id: I590ac4604b61fc1ffe7aba2ed89f8139847ccac3

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

@@ -110,7 +110,7 @@ final class PackWriterBitmapWalker {
 		}
 
 		if (marked) {
-			BitmapRevFilter filter = newRevFilter(seen, bitmapResult);
+			RevFilter filter = newRevFilter(seen, bitmapResult);
 			walker.setRevFilter(filter);
 
 			while (walker.next() != null) {
@@ -141,41 +141,89 @@ final class PackWriterBitmapWalker {
 		walker.reset();
 	}
 
-	static BitmapRevFilter newRevFilter(
-			final BitmapBuilder seen, final BitmapBuilder bitmapResult) {
+	static RevFilter newRevFilter(BitmapBuilder seen, BitmapBuilder bitmapResult) {
 		if (seen != null) {
-			return new BitmapRevFilter() {
-				protected boolean load(RevCommit cmit) {
-					if (seen.contains(cmit))
+			return new AddUnseenToBitmapFilter(seen, bitmapResult);
+		}
+		return new AddToBitmapFilter(bitmapResult);
+	}
+
+	/**
+	 * A RevFilter that adds the visited commits to {@code bitmap} as a side
+	 * effect.
+	 * <p>
+	 * When the walk hits a commit that is part of {@code bitmap}'s
+	 * BitmapIndex, that entire bitmap is ORed into {@code bitmap} and the
+	 * commit and its parents are marked as SEEN so that the walk does not
+	 * have to visit its ancestors.  This ensures the walk is very short if
+	 * there is good bitmap coverage.
+	 */
+	private static class AddToBitmapFilter extends RevFilter {
+		private final BitmapBuilder bitmap;
+
+		AddToBitmapFilter(BitmapBuilder bitmap) {
+			this.bitmap = bitmap;
+		}
+
+		@Override
+		public final boolean include(RevWalk walker, RevCommit cmit) {
+			if (bitmap.add(cmit, Constants.OBJ_COMMIT)) {
+				return true;
+			}
+			for (RevCommit p : cmit.getParents()) {
+				p.add(RevFlag.SEEN);
+			}
 			return false;
-					return bitmapResult.add(cmit, Constants.OBJ_COMMIT);
 		}
-			};
+
+		@Override
+		public final RevFilter clone() {
+			throw new UnsupportedOperationException();
 		}
-		return new BitmapRevFilter() {
+
 		@Override
-			protected boolean load(RevCommit cmit) {
-				return bitmapResult.add(cmit, Constants.OBJ_COMMIT);
+		public final boolean requiresCommitBody() {
+			return false;
 		}
-		};
 	}
 
-	static abstract class BitmapRevFilter extends RevFilter {
-		protected abstract boolean load(RevCommit cmit);
+	/**
+	 * A RevFilter that adds the visited commits to {@code bitmap} as a side
+	 * effect.
+	 * <p>
+	 * When the walk hits a commit that is part of {@code bitmap}'s
+	 * BitmapIndex, that entire bitmap is ORed into {@code bitmap} and the
+	 * commit and its parents are marked as SEEN so that the walk does not
+	 * have to visit its ancestors.  This ensures the walk is very short if
+	 * there is good bitmap coverage.
+	 * <p>
+	 * Commits named in {@code seen} are considered already seen.  If one is
+	 * encountered, that commit and its parents will be marked with the SEEN
+	 * flag to prevent the walk from visiting its ancestors.
+	 */
+	private static class AddUnseenToBitmapFilter extends RevFilter {
+		private final BitmapBuilder seen;
+		private final BitmapBuilder bitmap;
+
+		AddUnseenToBitmapFilter(BitmapBuilder seen, BitmapBuilder bitmapResult) {
+			this.seen = seen;
+			this.bitmap = bitmapResult;
+		}
 
 		@Override
 		public final boolean include(RevWalk walker, RevCommit cmit) {
-			if (load(cmit)) {
+			if (!seen.contains(cmit) && bitmap.add(cmit, Constants.OBJ_COMMIT)) {
 				return true;
 			}
-			for (RevCommit p : cmit.getParents())
+			for (RevCommit p : cmit.getParents()) {
 				p.add(RevFlag.SEEN);
+			}
 			return false;
 		}
 
 		@Override
 		public final RevFilter clone() {
-			return this;
+			throw new UnsupportedOperationException();
 		}
 
 		@Override