Make PackInserter public

The intent with the setCompressionLevel and checkExisting methods (which
are already public) is for callers to be able to call them, but they
can't do that if the class itself is not public.

Change-Id: I014044fec3bfa1d33775500345efd60eb5d45bde

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/PackInserter.java

@@ -99,7 +99,7 @@ import org.eclipse.jgit.util.sha1.SHA1;
  * Object inserter that inserts one pack per call to {@link #flush()}, and never
  * inserts loose objects.
  */
-class PackInserter extends ObjectInserter {
+public class PackInserter extends ObjectInserter {
 	/** Always produce version 2 indexes, to get CRC data. */
 	private static final int INDEX_VERSION = 2;