Do not send empty blob in response to blob:none filter

If I create a repository containing an empty file and clone it
with

	git clone --no-checkout --filter=blob:none \
		https://url/of/repository

then I would expect no blobs to be transferred over the wire.  Alas,
JGit rewrites filter=blob:none to filter=blob:limit=0, so if the
repository contains an empty file then the empty blob gets
transferred.

Fix it by teaching JGit about filters based on object type to
complement the existing filters based on object size.  This prepares
us for other future filters such as object:none.

In particular, this means we do not need to look up the size of the
filtered blobs, which should speed up clones.  Noticed by Anna
Pologova and Terry Parker.

Change-Id: Id4b234921a190c108d8be2c87f54dcbfa811602a
Signed-off-by: Jonathan Nieder <jrn@google.com>

3 files changed, 26 insertions, 2 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV0ParserTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV0ParserTest.java
index 965a2faf8e..c0db83a820 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV0ParserTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV0ParserTest.java
@@ -9,6 +9,10 @@
  */
 package org.eclipse.jgit.transport;
 
+import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
+import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
+import static org.eclipse.jgit.lib.Constants.OBJ_TAG;
+import static org.eclipse.jgit.lib.Constants.OBJ_TREE;
 import static org.eclipse.jgit.transport.ObjectIdMatcher.hasOnlyObjectIds;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.Assert.assertEquals;
@@ -160,6 +164,10 @@ public class ProtocolV0ParserTest {
 		assertThat(request.getWantIds(),
 				hasOnlyObjectIds("4624442d68ee402a94364191085b77137618633e",
 						"f900c8326a43303685c46b279b9f70411bff1a4b"));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_BLOB));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TREE));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_COMMIT));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TAG));
 		assertEquals(13000, request.getFilterSpec().getBlobLimit());
 		assertEquals(-1, request.getFilterSpec().getTreeDepthLimit());
 	}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV2ParserTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV2ParserTest.java
index 038ce717b3..837bdce919 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV2ParserTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/ProtocolV2ParserTest.java
@@ -9,6 +9,10 @@
  */
 package org.eclipse.jgit.transport;
 
+import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
+import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
+import static org.eclipse.jgit.lib.Constants.OBJ_TAG;
+import static org.eclipse.jgit.lib.Constants.OBJ_TREE;
 import static org.eclipse.jgit.transport.ObjectIdMatcher.hasOnlyObjectIds;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.hasItems;
@@ -195,7 +199,11 @@ public class ProtocolV2ParserTest {
 		ProtocolV2Parser parser = new ProtocolV2Parser(
 				ConfigBuilder.start().allowFilter().done());
 		FetchV2Request request = parser.parseFetchRequest(pckIn);
-		assertEquals(0, request.getFilterSpec().getBlobLimit());
+		assertFalse(request.getFilterSpec().allowsType(OBJ_BLOB));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TREE));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_COMMIT));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TAG));
+		assertEquals(-1, request.getFilterSpec().getBlobLimit());
 		assertEquals(-1, request.getFilterSpec().getTreeDepthLimit());
 	}
 
@@ -207,6 +215,10 @@ public class ProtocolV2ParserTest {
 		ProtocolV2Parser parser = new ProtocolV2Parser(
 				ConfigBuilder.start().allowFilter().done());
 		FetchV2Request request = parser.parseFetchRequest(pckIn);
+		assertTrue(request.getFilterSpec().allowsType(OBJ_BLOB));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TREE));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_COMMIT));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TAG));
 		assertEquals(15, request.getFilterSpec().getBlobLimit());
 		assertEquals(-1, request.getFilterSpec().getTreeDepthLimit());
 	}
@@ -219,6 +231,10 @@ public class ProtocolV2ParserTest {
 		ProtocolV2Parser parser = new ProtocolV2Parser(
 				ConfigBuilder.start().allowFilter().done());
 		FetchV2Request request = parser.parseFetchRequest(pckIn);
+		assertTrue(request.getFilterSpec().allowsType(OBJ_BLOB));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TREE));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_COMMIT));
+		assertTrue(request.getFilterSpec().allowsType(OBJ_TAG));
 		assertEquals(-1, request.getFilterSpec().getBlobLimit());
 		assertEquals(3, request.getFilterSpec().getTreeDepthLimit());
 	}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java
index bb33eefcee..e9b4af932e 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/UploadPackTest.java
@@ -127,7 +127,7 @@ public class UploadPackTest {
 	}
 
 	@Test
-	public void testFetchWithBlobNoneFilter() throws Exception {
+	public void testFetchWithBlobZeroFilter() throws Exception {
 		InMemoryRepository server2 = newRepo("server2");
 		try (TestRepository<InMemoryRepository> remote2 = new TestRepository<>(
 				server2)) {