NoteMapTest: Open TreeWalk instances in try-with-resource

Change-Id: I70da0140fe087e7e69c28e9ddd125495d916ec1b
Signed-off-by: David Pursehouse <david.pursehouse@sonymobile.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/notes/NoteMapTest.java

@@ -403,10 +403,12 @@ public class NoteMapTest extends RepositoryTestCase {
 		}
 
 		RevCommit n = commitNoteMap(map);
-		TreeWalk tw = new TreeWalk(reader);
-		tw.reset(n.getTree());
-		while (tw.next())
-			assertFalse("no fan-out subtree", tw.isSubtree());
+		try (TreeWalk tw = new TreeWalk(reader)) {
+			tw.reset(n.getTree());
+			while (tw.next()) {
+				assertFalse("no fan-out subtree", tw.isSubtree());
+			}
+		}
 
 		for (int i = 254; i < 256; i++) {
 			idBuf.setByte(Constants.OBJECT_ID_LENGTH - 1, i);
@@ -418,13 +420,15 @@ public class NoteMapTest extends RepositoryTestCase {
 
 		// The 00 bucket is fully split.
 		String path = fanout(38, idBuf.name());
-		tw = TreeWalk.forPath(reader, path, n.getTree());
-		assertNotNull("has " + path, tw);
+		try (TreeWalk tw = TreeWalk.forPath(reader, path, n.getTree())) {
+			assertNotNull("has " + path, tw);
+		}
 
 		// The other bucket is not.
 		path = fanout(2, data1.name());
-		tw = TreeWalk.forPath(reader, path, n.getTree());
-		assertNotNull("has " + path, tw);
+		try (TreeWalk tw = TreeWalk.forPath(reader, path, n.getTree())) {
+			assertNotNull("has " + path, tw);
+		}
 	}
 
 	@Test