Correctly skip over unrecognized optional dircache extensions

We didn't skip the correct number of bytes when we skipped over an
unrecognized but optional dircache extension.  We missed skipping
the 8 byte header that makes up the extension's name and length.

We also didn't include the skipped extension's payload as part of
our index checksum, resuting in a checksum failure when the index
was done reading.  So ensure we always scan through a skipped
section and include it in the checksum computation.

Add a test case for a currently unsupported index extension, 'ZZZZ',
to verify we can still read the DirCache object even though we
don't know what 'ZZZZ' is supposed to mean.

Bug: 301287
Change-Id: I4bdde94576fffe826d0782483fd98cab1ea628fa
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheCGitCompatabilityTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheCGitCompatabilityTest.java
index 688fa73598..fa5fea8633 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheCGitCompatabilityTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/dircache/DirCacheCGitCompatabilityTest.java
@@ -52,6 +52,7 @@ import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.junit.LocalDiskRepositoryTestCase;
 import org.eclipse.jgit.lib.FileMode;
 import org.eclipse.jgit.lib.ObjectId;
@@ -100,6 +101,34 @@ public class DirCacheCGitCompatabilityTest extends LocalDiskRepositoryTestCase {
 		}
 	}
 
+	public void testUnsupportedOptionalExtension() throws Exception {
+		final DirCache dc = new DirCache(pathOf("gitgit.index.ZZZZ"));
+		dc.read();
+		assertEquals(1, dc.getEntryCount());
+		assertEquals("A", dc.getEntry(0).getPathString());
+	}
+
+	public void testUnsupportedRequiredExtension() throws Exception {
+		final DirCache dc = new DirCache(pathOf("gitgit.index.aaaa"));
+		try {
+			dc.read();
+			fail("Cache loaded an unsupported extension");
+		} catch (CorruptObjectException err) {
+			assertEquals("DIRC extension 'aaaa'"
+					+ " not supported by this version.", err.getMessage());
+		}
+	}
+
+	public void testCorruptChecksumAtFooter() throws Exception {
+		final DirCache dc = new DirCache(pathOf("gitgit.index.badchecksum"));
+		try {
+			dc.read();
+			fail("Cache loaded despite corrupt checksum");
+		} catch (CorruptObjectException err) {
+			assertEquals("DIRC checksum mismatch", err.getMessage());
+		}
+	}
+
 	private static void assertEqual(final CGitIndexRecord c,
 			final DirCacheEntry j) {
 		assertNotNull(c);