Fix MissingObjectException in RenameDetector

When attempting to determine the size of a blob that does not exist,
the RenameDetector throws a MissingObjectException.

The fix is to return a size of zero if the size is requested for a blob
id that doesn't exist.

Bug: 481577
Change-Id: I4e86276039c630617610cc51d0eefa56d7d3952f
Signed-off-by: Rüdiger Herrmann <ruediger.herrmann@gmx.de>

org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/RenameDetectorTest.java

@@ -48,6 +48,7 @@ import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
+import java.util.Arrays;
 import java.util.List;
 
 import org.eclipse.jgit.diff.DiffEntry.ChangeType;
@@ -226,6 +227,19 @@ public class RenameDetectorTest extends RepositoryTestCase {
 		assertCopy(d, b, 100, entries.get(2));
 	}
 
+	@Test
+	public void testExactRename_UnstagedFile() throws Exception {
+		ObjectId aId = blob("foo");
+		DiffEntry a = DiffEntry.delete(PATH_A, aId);
+		DiffEntry b = DiffEntry.add(PATH_B, aId);
+
+		rd.addAll(Arrays.asList(a, b));
+		List<DiffEntry> entries = rd.compute();
+
+		assertEquals(1, entries.size());
+		assertRename(a, b, 100, entries.get(0));
+	}
+
 	@Test
 	public void testInexactRename_OnePair() throws Exception {
 		ObjectId aId = blob("foo\nbar\nbaz\nblarg\n");
@@ -429,6 +443,23 @@ public class RenameDetectorTest extends RepositoryTestCase {
 		assertSame(b, entries.get(1));
 	}
 
+	@Test
+	public void testNoRenames_UntrackedFile() throws Exception {
+		ObjectId aId = blob("foo");
+		ObjectId bId = ObjectId
+				.fromString("3049eb6eee7e1318f4e78e799bf33f1e54af9cbf");
+
+		DiffEntry a = DiffEntry.delete(PATH_A, aId);
+		DiffEntry b = DiffEntry.add(PATH_B, bId);
+
+		rd.addAll(Arrays.asList(a, b));
+		List<DiffEntry> entries = rd.compute();
+
+		assertEquals(2, entries.size());
+		assertSame(a, entries.get(0));
+		assertSame(b, entries.get(1));
+	}
+
 	@Test
 	public void testBreakModify_BreakAll() throws Exception {
 		ObjectId aId = blob("foo");

org.eclipse.jgit/src/org/eclipse/jgit/diff/ContentSource.java

@@ -132,7 +132,11 @@ public abstract class ContentSource {
 
 		@Override
 		public long size(String path, ObjectId id) throws IOException {
-			return reader.getObjectSize(id, Constants.OBJ_BLOB);
+			try {
+				return reader.getObjectSize(id, Constants.OBJ_BLOB);
+			} catch (MissingObjectException ignore) {
+				return 0;
+			}
 		}
 
 		@Override