Add the intended file to avoid breakage

This case breaks when the default is to disallow empty commits.

Change-Id: Ibc223092eefe9f4b21374717dee5a9399bf890f9

org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/ResolveMergerTest.java

@@ -89,7 +89,7 @@ public class ResolveMergerTest extends RepositoryTestCase {
 		file = new File(db.getWorkTree(), "unrelated.txt");
 		write(file, "unrelated");
 
-		git.add().addFilepattern("unrelated").call();
+		git.add().addFilepattern("unrelated.txt").call();
 		RevCommit head = git.commit().setMessage("Adding another file").call();
 
 		// Untracked file to cause failing path for delete() of folder1