BundleWriter: Always use OFS_DELTA

CGit just learned to always use OFS_DELTA when writing out bundle
files.  This makes sense because bundle came about well after
OFS_DELTA was established, so any version of CGit that can read a
bundle file can also read OFS_DELTA.  Since OFS_DELTA is smaller,
always use it when writing bundles.

Change-Id: I44f9921494798ea0c99e16eab58b87bebeb9aff5
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/transport/BundleWriter.java

@@ -190,6 +190,7 @@ public class BundleWriter {
 			inc.addAll(include.values());
 			for (final RevCommit r : assume)
 				exc.add(r.getId());
+			packWriter.setDeltaBaseAsOffset(true);
 			packWriter.setThin(exc.size() > 0);
 			packWriter.preparePack(monitor, inc, exc);