Teach UploadPack "ofs-delta" in "fetch"

Add support for the "ofs-delta" parameter in the "fetch" command in
the fetch-pack/upload-pack protocol v2.

Change-Id: I728cf986082fce4ddeb6a6435897692e15e60cc7
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java

@@ -518,15 +518,18 @@ public class UploadPackTest {
 	 * Parse multiplexed packfile output from upload-pack using protocol V2
 	 * into the client repository.
 	 */
-	private void parsePack(ByteArrayInputStream recvStream) throws Exception {
-		parsePack(recvStream, NullProgressMonitor.INSTANCE);
+	private ReceivedPackStatistics parsePack(ByteArrayInputStream recvStream) throws Exception {
+		return parsePack(recvStream, NullProgressMonitor.INSTANCE);
 	}
 
-	private void parsePack(ByteArrayInputStream recvStream, ProgressMonitor pm)
+	private ReceivedPackStatistics parsePack(ByteArrayInputStream recvStream, ProgressMonitor pm)
 			throws Exception {
 		SideBandInputStream sb = new SideBandInputStream(
-				recvStream, pm, new StringWriter(), NullOutputStream.INSTANCE);
-		client.newObjectInserter().newPackParser(sb).parse(NullProgressMonitor.INSTANCE);
+				recvStream, pm,
+				new StringWriter(), NullOutputStream.INSTANCE);
+		PackParser pp = client.newObjectInserter().newPackParser(sb);
+		pp.parse(NullProgressMonitor.INSTANCE);
+		return pp.getReceivedPackStatistics();
 	}
 
 	@Test
@@ -838,6 +841,42 @@ public class UploadPackTest {
 		assertTrue(client.hasObject(tag.toObjectId()));
 	}
 
+	@Test
+	public void testV2FetchOfsDelta() throws Exception {
+		String commonInBlob = "abcdefghijklmnopqrstuvwxyz";
+
+		RevBlob parentBlob = remote.blob(commonInBlob + "a");
+		RevCommit parent = remote.commit(remote.tree(remote.file("foo", parentBlob)));
+		RevBlob childBlob = remote.blob(commonInBlob + "b");
+		RevCommit child = remote.commit(remote.tree(remote.file("foo", childBlob)), parent);
+		remote.update("branch1", child);
+
+		// Without ofs-delta.
+		ByteArrayInputStream recvStream = uploadPackV2(
+			"command=fetch\n",
+			PacketLineIn.DELIM,
+			"want " + child.toObjectId().getName() + "\n",
+			"done\n",
+			PacketLineIn.END);
+		PacketLineIn pckIn = new PacketLineIn(recvStream);
+		assertThat(pckIn.readString(), is("packfile"));
+		ReceivedPackStatistics stats = parsePack(recvStream);
+		assertTrue(stats.getNumOfsDelta() == 0);
+
+		// With ofs-delta.
+		recvStream = uploadPackV2(
+			"command=fetch\n",
+			PacketLineIn.DELIM,
+			"want " + child.toObjectId().getName() + "\n",
+			"ofs-delta\n",
+			"done\n",
+			PacketLineIn.END);
+		pckIn = new PacketLineIn(recvStream);
+		assertThat(pckIn.readString(), is("packfile"));
+		stats = parsePack(recvStream);
+		assertTrue(stats.getNumOfsDelta() != 0);
+	}
+
 	private static class RejectAllRefFilter implements RefFilter {
 		@Override
 		public Map<String, Ref> filter(Map<String, Ref> refs) {

org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java

@@ -967,6 +967,8 @@ public class UploadPack {
 			} else if (line.equals(OPTION_INCLUDE_TAG)) {
 				options.add(OPTION_INCLUDE_TAG);
 				includeTag = true;
+			} else if (line.equals(OPTION_OFS_DELTA)) {
+				options.add(OPTION_OFS_DELTA);
 			}
 			// else ignore it
 		}