reftable: read file footer in ReftableReader#allRefs

allRefs determined the end of the ref block without accounting for
index or log blocks. This could cause other blocks to be interpreted
as ref blocks, leading to "invalid block" error messages.

Change-Id: I7b9323e7d5e0e7d64535b3ec1efd576aed1e9870
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

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

@@ -566,6 +566,44 @@ public class ReftableTest {
 		assertEquals(all, more);
 	}
 
+	@Test
+	public void allRefs() throws IOException {
+		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
+		ReftableConfig cfg = new ReftableConfig();
+		cfg.setRefBlockSize(1024);
+		cfg.setLogBlockSize(1024);
+		cfg.setAlignBlocks(true);
+		ReftableWriter writer = new ReftableWriter()
+				.setMinUpdateIndex(1)
+				.setMaxUpdateIndex(1)
+				.setConfig(cfg)
+				.begin(buffer);
+		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
+
+		// Fill out the 1st ref block.
+		List<String> names = new ArrayList<>();
+		for (int i = 0; i < 4; i++) {
+			String name = new String(new char[220]).replace("\0", String.format("%c", i + 'a'));
+			names.add(name);
+			writer.writeRef(ref(name, i));
+		}
+
+		// Add some log data.
+		writer.writeLog(MASTER, 1, who, ObjectId.zeroId(), id(1), "msg");
+		writer.finish();
+		byte[] table = buffer.toByteArray();
+
+		ReftableReader t = read(table);
+		RefCursor c = t.allRefs();
+
+		int j = 0;
+		while (c.next()) {
+			assertEquals(names.get(j), c.getRef().getName());
+			j++;
+		}
+	}
+
+
 	@Test
 	public void reflogSeek() throws IOException {
 		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableReader.java

@@ -169,11 +169,13 @@ public class ReftableReader extends Reftable {
 			readFileHeader();
 		}
 
-		long end = refEnd > 0 ? refEnd : (src.size() - FILE_FOOTER_LEN);
-		src.adviseSequentialRead(0, end);
+		if (refEnd == 0) {
+			readFileFooter();
+		}
+		src.adviseSequentialRead(0, refEnd);
 
-		RefCursorImpl i = new RefCursorImpl(end, null, false);
-		i.block = readBlock(0, end);
+		RefCursorImpl i = new RefCursorImpl(refEnd, null, false);
+		i.block = readBlock(0, refEnd);
 		return i;
 	}