TreeFormatter: disallow empty filenames in trees

Git barfs on these (and they don't make any sense), so we certainly
shouldn't write them.

Change-Id: I3faf8554a05f0fd147be2e63fbe55987d3f88099
Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/T0003_BasicTest.java

@@ -82,9 +82,13 @@
 import org.eclipse.jgit.storage.file.FileRepositoryBuilder;
 import org.eclipse.jgit.test.resources.SampleDataRepositoryTestCase;
 import org.eclipse.jgit.util.FileUtils;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 public class T0003_BasicTest extends SampleDataRepositoryTestCase {
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
 
 	@Test
 	public void test001_Initalize() {
@@ -325,6 +329,17 @@ public void test002_WriteEmptyTree2() throws IOException {
 		assertFalse("Exists " + o, o.isFile());
 	}
 
+	@Test
+	public void test002_CreateBadTree() throws Exception {
+		// We won't create a tree entry with an empty filename
+		//
+		expectedException.expect(IllegalArgumentException.class);
+		expectedException.expectMessage(JGitText.get().invalidTreeZeroLengthName);
+		final TreeFormatter formatter = new TreeFormatter();
+		formatter.append("", FileMode.TREE,
+				ObjectId.fromString("4b825dc642cb6eb9a060e54bf8d69288fbee4904"));
+	}
+
 	@Test
 	public void test006_ReadUglyConfig() throws IOException,
 			ConfigInvalidException {

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutMaliciousPathTest.java

@@ -366,7 +366,9 @@ private void testMaliciousPath(boolean good, boolean secondCheckout,
 			insertId = blobId;
 			for (int i = path.length - 1; i >= 0; --i) {
 				TreeFormatter treeFormatter = new TreeFormatter();
-				treeFormatter.append(path[i], mode, insertId);
+				treeFormatter.append(path[i].getBytes(), 0,
+							path[i].getBytes().length,
+							mode, insertId, true);
 				insertId = newObjectInserter.insert(treeFormatter);
 				mode = FileMode.TREE;
 			}

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -367,6 +367,7 @@ invalidTagOption=Invalid tag option: {0}
 invalidTimeout=Invalid timeout: {0}
 invalidTimeUnitValue2=Invalid time unit value: {0}.{1}={2}
 invalidTimeUnitValue3=Invalid time unit value: {0}.{1}.{2}={3}
+invalidTreeZeroLengthName=Cannot append a tree entry with zero-length name
 invalidURL=Invalid URL {0}
 invalidWildcards=Invalid wildcards {0}
 invalidRefSpec=Invalid refspec {0}

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -425,6 +425,7 @@ public static JGitText get() {
 	/***/ public String invalidTimeout;
 	/***/ public String invalidTimeUnitValue2;
 	/***/ public String invalidTimeUnitValue3;
+	/***/ public String invalidTreeZeroLengthName;
 	/***/ public String invalidURL;
 	/***/ public String invalidWildcards;
 	/***/ public String invalidRefSpec;

org.eclipse.jgit/src/org/eclipse/jgit/lib/TreeFormatter.java

@@ -53,6 +53,7 @@
 import java.io.IOException;
 
 import org.eclipse.jgit.errors.CorruptObjectException;
+import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevTree;
@@ -193,6 +194,34 @@ public void append(byte[] name, FileMode mode, AnyObjectId id) {
 	 */
 	public void append(byte[] nameBuf, int namePos, int nameLen, FileMode mode,
 			AnyObjectId id) {
+		append(nameBuf, namePos, nameLen, mode, id, false);
+	}
+
+	/**
+	 * Append any entry to the tree.
+	 *
+	 * @param nameBuf
+	 *            buffer holding the name of the entry. The name should be UTF-8
+	 *            encoded, but file name encoding is not a well defined concept
+	 *            in Git.
+	 * @param namePos
+	 *            first position within {@code nameBuf} of the name data.
+	 * @param nameLen
+	 *            number of bytes from {@code nameBuf} to use as the name.
+	 * @param mode
+	 *            mode describing the treatment of {@code id}.
+	 * @param id
+	 *            the ObjectId to store in this entry.
+	 * @param allowEmptyName
+	 *            allow an empty filename (creating a corrupt tree)
+	 * @since 4.6
+	 */
+	public void append(byte[] nameBuf, int namePos, int nameLen, FileMode mode,
+			AnyObjectId id, boolean allowEmptyName) {
+		if (nameLen == 0 && !allowEmptyName) {
+			throw new IllegalArgumentException(
+					JGitText.get().invalidTreeZeroLengthName);
+		}
 		if (fmtBuf(nameBuf, namePos, nameLen, mode)) {
 			id.copyRawTo(buf, ptr);
 			ptr += OBJECT_ID_LENGTH;