DiffFormatterTest: Add a test to confirm the default rename detection settings

Add a test that confirms:

- No rename detector is initialized by default

- Rename detector is initialized after calling setDetectRenames(true)

- Rename limit and rename score have the default values 400 and
  60, respectively. Note that there are no constants for these values
  so the test hard codes them.

Change-Id: I327e2b348a40ef67d8a184e5ab09f4e9ab573e1c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffFormatterTest.java

 package org.eclipse.jgit.diff;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 
 import java.io.BufferedOutputStream;
 import java.io.ByteArrayOutputStream;
 		super.tearDown();
 	}
 
+	@Test
+	public void testDefaultRenameDetectorSettings() throws Exception {
+		RenameDetector rd = df.getRenameDetector();
+		assertNull(rd);
+		df.setDetectRenames(true);
+		rd = df.getRenameDetector();
+		assertNotNull(rd);
+		assertEquals(400, rd.getRenameLimit());
+		assertEquals(60, rd.getRenameScore());
+	}
+
 	@Test
 	public void testCreateFileHeader_Add() throws Exception {
 		ObjectId adId = blob("a\nd\n");