upload-pack: teach deepen-relative in protocol v2

Commit 685fbd3291 ("fetch-pack: perform a fetch using v2", 2018-03-15)
attempted to teach Git deepen-relative in protocol v2 (among other
things), but it didn't work:

 (1) fetch-pack.c needs to emit "deepen-relative".
 (2) upload-pack.c needs to ensure that the correct deepen_relative
     variable is passed to deepen() (there are two - the static variable
     and the one in struct upload_pack_data).
 (3) Before deepen() computes the list of reachable shallows, it first
     needs to mark all "our" refs as OUR_REF. v2 currently does not do
     this, because unlike v0, it is not needed otherwise.

Fix all this and include a test demonstrating that it works now. For
(2), the static variable deepen_relative is also eliminated, removing a
source of confusion.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Reviewed-by: Josh Steadmon <steadmon@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

fetch-pack.c

@@ -1007,6 +1007,8 @@ static void add_shallow_requests(struct strbuf *req_buf,
 			packet_buf_write(req_buf, "deepen-not %s", s->string);
 		}
 	}
+	if (args->deepen_relative)
+		packet_buf_write(req_buf, "deepen-relative\n");
 }
 
 static void add_wants(int no_dependents, const struct ref *wants, struct strbuf *req_buf)

t/t5702-protocol-v2.sh

@@ -489,6 +489,35 @@ test_expect_success 'ensure that multiple fetches in same process from a shallow
 	grep "fetch< version 2" trace
 '
 
+test_expect_success 'deepen-relative' '
+	rm -rf server client trace &&
+
+	test_create_repo server &&
+	test_commit -C server one &&
+	test_commit -C server two &&
+	test_commit -C server three &&
+	git clone --depth 1 "file://$(pwd)/server" client &&
+	test_commit -C server four &&
+
+	# Sanity check that only "three" is downloaded
+	git -C client log --pretty=tformat:%s master >actual &&
+	echo three >expected &&
+	test_cmp expected actual &&
+
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client -c protocol.version=2 \
+		fetch --deepen=1 origin &&
+	# Ensure that protocol v2 is used
+	grep "fetch< version 2" trace &&
+
+	git -C client log --pretty=tformat:%s origin/master >actual &&
+	cat >expected <<-\EOF &&
+	four
+	three
+	two
+	EOF
+	test_cmp expected actual
+'
+
 # Test protocol v2 with 'http://' transport
 #
 . "$TEST_DIRECTORY"/lib-httpd.sh

upload-pack.c

@@ -43,7 +43,6 @@
 
 static timestamp_t oldest_have;
 
-static int deepen_relative;
 static int multi_ack;
 static int no_done;
 static int use_thin_pack, use_ofs_delta, use_include_tag;
@@ -662,6 +661,9 @@ static void send_unshallow(const struct object_array *shallows,
 	}
 }
 
+static int check_ref(const char *refname_full, const struct object_id *oid,
+		     int flag, void *cb_data);
+
 static void deepen(int depth, int deepen_relative,
 		   struct object_array *shallows, struct object_array *want_obj)
 {
@@ -676,6 +678,13 @@ static void deepen(int depth, int deepen_relative,
 		struct object_array reachable_shallows = OBJECT_ARRAY_INIT;
 		struct commit_list *result;
 
+		/*
+		 * Checking for reachable shallows requires that our refs be
+		 * marked with OUR_REF.
+		 */
+		head_ref_namespaced(check_ref, NULL);
+		for_each_namespaced_ref(check_ref, NULL);
+
 		get_reachable_list(shallows, &reachable_shallows);
 		result = get_shallow_commits(&reachable_shallows,
 					     depth + 1,
@@ -712,6 +721,7 @@ static void deepen_by_rev_list(int ac, const char **av,
 static int send_shallow_list(int depth, int deepen_rev_list,
 			     timestamp_t deepen_since,
 			     struct string_list *deepen_not,
+			     int deepen_relative,
 			     struct object_array *shallows,
 			     struct object_array *want_obj)
 {
@@ -834,6 +844,7 @@ static void receive_needs(struct object_array *want_obj)
 	int has_non_tip = 0;
 	timestamp_t deepen_since = 0;
 	int deepen_rev_list = 0;
+	int deepen_relative = 0;
 
 	shallow_nr = 0;
 	for (;;) {
@@ -925,7 +936,8 @@ static void receive_needs(struct object_array *want_obj)
 		return;
 
 	if (send_shallow_list(depth, deepen_rev_list, deepen_since,
-			      &deepen_not, &shallows, want_obj))
+			      &deepen_not, deepen_relative, &shallows,
+			      want_obj))
 		packet_flush(1);
 	object_array_clear(&shallows);
 }
@@ -1398,6 +1410,7 @@ static void send_shallow_info(struct upload_pack_data *data,
 
 	if (!send_shallow_list(data->depth, data->deepen_rev_list,
 			       data->deepen_since, &data->deepen_not,
+			       data->deepen_relative,
 			       &data->shallows, want_obj) &&
 	    is_repository_shallow(the_repository))
 		deepen(INFINITE_DEPTH, data->deepen_relative, &data->shallows,