reftable: namespace unit tests

Add additional test cases for looking up entries within a namespace
such as refs/heads/ or refs/tags/, where the seek is passed a name
that ends with '/'.

Change-Id: I5f944de7518cd0090374bddba48d4dd3955a8d72

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java

@@ -74,6 +74,7 @@ import org.junit.Test;
 
 public class ReftableTest {
 	private static final String MASTER = "refs/heads/master";
+	private static final String NEXT = "refs/heads/next";
 	private static final String V1_0 = "refs/tags/v1.0";
 
 	private Stats stats;
@@ -273,6 +274,41 @@ public class ReftableTest {
 		}
 	}
 
+	@Test
+	public void namespaceNotFound() throws IOException {
+		Ref exp = ref(MASTER, 1);
+		ReftableReader t = read(write(exp));
+		try (RefCursor rc = t.seekRef("refs/changes/")) {
+			assertFalse(rc.next());
+		}
+		try (RefCursor rc = t.seekRef("refs/tags/")) {
+			assertFalse(rc.next());
+		}
+	}
+
+	@Test
+	public void namespaceHeads() throws IOException {
+		Ref master = ref(MASTER, 1);
+		Ref next = ref(NEXT, 2);
+		Ref v1 = tag(V1_0, 3, 4);
+
+		ReftableReader t = read(write(master, next, v1));
+		try (RefCursor rc = t.seekRef("refs/tags/")) {
+			assertTrue(rc.next());
+			assertEquals(V1_0, rc.getRef().getName());
+			assertFalse(rc.next());
+		}
+		try (RefCursor rc = t.seekRef("refs/heads/")) {
+			assertTrue(rc.next());
+			assertEquals(MASTER, rc.getRef().getName());
+
+			assertTrue(rc.next());
+			assertEquals(NEXT, rc.getRef().getName());
+
+			assertFalse(rc.next());
+		}
+	}
+
 	@SuppressWarnings("boxing")
 	@Test
 	public void indexScan() throws IOException {