Rename DfsPackFile getBitmap method to match PackFile

There is no reason for these to differ in name. Match the
shorter name used by PackFile.

Change-Id: I2d3a299069acc5ce276b1b5439ff2258903c6ff3

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsPackFile.java

@@ -276,7 +276,7 @@ public final class DfsPackFile {
 		}
 	}
 
-	PackBitmapIndex getPackBitmapIndex(DfsReader ctx) throws IOException {
+	PackBitmapIndex getBitmapIndex(DfsReader ctx) throws IOException {
 		DfsBlockCache.Ref<PackBitmapIndex> idxref = bitmapIndex;
 		if (idxref != null) {
 			PackBitmapIndex idx = idxref.get();

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsReader.java

@@ -146,7 +146,7 @@ public final class DfsReader extends ObjectReader implements ObjectReuseAsIs {
 	@Override
 	public BitmapIndex getBitmapIndex() throws IOException {
 		for (DfsPackFile pack : db.getPacks()) {
-			PackBitmapIndex bitmapIndex = pack.getPackBitmapIndex(this);
+			PackBitmapIndex bitmapIndex = pack.getBitmapIndex(this);
 			if (bitmapIndex != null)
 				return new BitmapIndexImpl(bitmapIndex);
 		}
@@ -156,7 +156,7 @@ public final class DfsReader extends ObjectReader implements ObjectReuseAsIs {
 	public Collection<CachedPack> getCachedPacksAndUpdate(
 		BitmapBuilder needBitmap) throws IOException {
 		for (DfsPackFile pack : db.getPacks()) {
-			PackBitmapIndex bitmapIndex = pack.getPackBitmapIndex(this);
+			PackBitmapIndex bitmapIndex = pack.getBitmapIndex(this);
 			if (needBitmap.removeAllOrNone(bitmapIndex))
 				return Collections.<CachedPack> singletonList(
 						new DfsCachedPack(pack));