Teach UploadPack "include-tag" in "fetch"

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

In order to determine which tags to include, only objects pointed to by
refs starting with "refs/tags/" are checked. This restriction is for
performance reasons and to match the behavior of Git (see add_ref_tag()
in builtin/pack-objects.c).

Change-Id: I7d70aa09bcc8a525218ff1559e286c2a610258ca
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Jonathan Nieder <jrn@google.com>

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

@@ -805,6 +805,39 @@ public class UploadPackTest {
 		assertTrue(sw.toString().isEmpty());
 	}
 
+	@Test
+	public void testV2FetchIncludeTag() throws Exception {
+		RevCommit commit = remote.commit().message("x").create();
+		RevTag tag = remote.tag("tag", commit);
+		remote.update("branch1", commit);
+		remote.update("refs/tags/tag", tag);
+
+		// Without include-tag.
+		ByteArrayInputStream recvStream = uploadPackV2(
+			"command=fetch\n",
+			PacketLineIn.DELIM,
+			"want " + commit.toObjectId().getName() + "\n",
+			"done\n",
+			PacketLineIn.END);
+		PacketLineIn pckIn = new PacketLineIn(recvStream);
+		assertThat(pckIn.readString(), is("packfile"));
+		parsePack(recvStream);
+		assertFalse(client.hasObject(tag.toObjectId()));
+
+		// With tag.
+		recvStream = uploadPackV2(
+			"command=fetch\n",
+			PacketLineIn.DELIM,
+			"want " + commit.toObjectId().getName() + "\n",
+			"include-tag\n",
+			"done\n",
+			PacketLineIn.END);
+		pckIn = new PacketLineIn(recvStream);
+		assertThat(pckIn.readString(), is("packfile"));
+		parsePack(recvStream);
+		assertTrue(client.hasObject(tag.toObjectId()));
+	}
+
 	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

@@ -43,6 +43,7 @@
 
 package org.eclipse.jgit.transport;
 
+import static org.eclipse.jgit.lib.Constants.R_TAGS;
 import static org.eclipse.jgit.lib.RefDatabase.ALL;
 import static org.eclipse.jgit.transport.GitProtocolConstants.COMMAND_FETCH;
 import static org.eclipse.jgit.transport.GitProtocolConstants.COMMAND_LS_REFS;
@@ -951,6 +952,7 @@ public class UploadPack {
 					.format(JGitText.get().unexpectedPacketLine, line));
 		}
 
+		boolean includeTag = false;
 		while ((line = pckIn.readString()) != PacketLineIn.END) {
 			if (line.startsWith("want ")) { //$NON-NLS-1$
 				wantIds.add(ObjectId.fromString(line.substring(5)));
@@ -962,6 +964,9 @@ public class UploadPack {
 				options.add(OPTION_THIN_PACK);
 			} else if (line.equals(OPTION_NO_PROGRESS)) {
 				options.add(OPTION_NO_PROGRESS);
+			} else if (line.equals(OPTION_INCLUDE_TAG)) {
+				options.add(OPTION_INCLUDE_TAG);
+				includeTag = true;
 			}
 			// else ignore it
 		}
@@ -990,7 +995,9 @@ public class UploadPack {
 				pckOut.writeDelim();
 			pckOut.writeString("packfile\n"); //$NON-NLS-1$
 			sendPack(new PackStatistics.Accumulator(),
-					refs == null ? null : refs.values());
+					includeTag
+						? db.getRefDatabase().getRefsByPrefix(R_TAGS)
+						: null);
 		}
 		pckOut.end();
 	}