Use a single ObjectReader in IpLogGenerator

This way we can be ensured its released when the generator
is done running.

Change-Id: I6be48d26b9bd5ac176c1316a9aabdf3a897e1696
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit.iplog/src/org/eclipse/jgit/iplog/IpLogGenerator.java

@@ -183,8 +183,8 @@ public class IpLogGenerator {
 		try {
 			db = repo;
 			curs = db.newObjectReader();
-			rw = new RevWalk(db);
-			tw = new NameConflictTreeWalk(db);
+			rw = new RevWalk(curs);
+			tw = new NameConflictTreeWalk(curs);
 
 			RevCommit c = rw.parseCommit(startCommit);