Merge branch 'jt/avoid-ls-refs'

Over some transports, fetching objects with an exact commit object
name can be done without first seeing the ref advertisements.  The
code has been optimized to exploit this.

* jt/avoid-ls-refs:
  fetch: do not list refs if fetching only hashes
  transport: list refs before fetch if necessary
  transport: do not list refs if possible
  transport: allow skipping of ref listing

builtin/fetch.c

@@ -1186,6 +1186,7 @@ static int do_fetch(struct transport *transport,
 	int retcode = 0;
 	const struct ref *remote_refs;
 	struct argv_array ref_prefixes = ARGV_ARRAY_INIT;
+	int must_list_refs = 1;
 
 	if (tags == TAGS_DEFAULT) {
 		if (transport->remote->fetch_tags == 2)
@@ -1201,17 +1202,36 @@ static int do_fetch(struct transport *transport,
 			goto cleanup;
 	}
 
-	if (rs->nr)
+	if (rs->nr) {
+		int i;
+
 		refspec_ref_prefixes(rs, &ref_prefixes);
-	else if (transport->remote && transport->remote->fetch.nr)
+
+		/*
+		 * We can avoid listing refs if all of them are exact
+		 * OIDs
+		 */
+		must_list_refs = 0;
+		for (i = 0; i < rs->nr; i++) {
+			if (!rs->items[i].exact_sha1) {
+				must_list_refs = 1;
+				break;
+			}
+		}
+	} else if (transport->remote && transport->remote->fetch.nr)
 		refspec_ref_prefixes(&transport->remote->fetch, &ref_prefixes);
 
-	if (ref_prefixes.argc &&
-	    (tags == TAGS_SET || (tags == TAGS_DEFAULT))) {
+	if (tags == TAGS_SET || tags == TAGS_DEFAULT) {
+		must_list_refs = 1;
+		if (ref_prefixes.argc)
 			argv_array_push(&ref_prefixes, "refs/tags/");
 	}
 
+	if (must_list_refs)
 		remote_refs = transport_get_remote_refs(transport, &ref_prefixes);
+	else
+		remote_refs = NULL;
+
 	argv_array_clear(&ref_prefixes);
 
 	ref_map = get_ref_map(transport->remote, remote_refs, rs,

fetch-pack.c

@@ -1626,7 +1626,7 @@ struct ref *fetch_pack(struct fetch_pack_args *args,
 		parse_list_objects_filter(&args->filter_options, "blob:none");
 	}
 
-	if (!ref) {
+	if (version != protocol_v2 && !ref) {
 		packet_flush(fd[1]);
 		die(_("no matching remote head"));
 	}

t/t5551-http-fetch-smart.sh

@@ -381,6 +381,21 @@ test_expect_success 'using fetch command in remote-curl updates refs' '
 	test_cmp expect actual
 '
 
+test_expect_success 'fetch by SHA-1 without tag following' '
+	SERVER="$HTTPD_DOCUMENT_ROOT_PATH/server" &&
+	rm -rf "$SERVER" client &&
+
+	git init "$SERVER" &&
+	test_commit -C "$SERVER" foo &&
+
+	git clone $HTTPD_URL/smart/server client &&
+
+	test_commit -C "$SERVER" bar &&
+	git -C "$SERVER" rev-parse bar >bar_hash &&
+	git -C client -c protocol.version=0 fetch \
+		--no-tags origin $(cat bar_hash)
+'
+
 test_expect_success 'GIT_REDACT_COOKIES redacts cookies' '
 	rm -rf clone &&
 	echo "Set-Cookie: Foo=1" >cookies &&

t/t5702-protocol-v2.sh

@@ -79,6 +79,19 @@ test_expect_success 'fetch with git:// using protocol v2' '
 	grep "fetch< version 2" log
 '
 
+test_expect_success 'fetch by hash without tag following with protocol v2 does not list refs' '
+	test_when_finished "rm -f log" &&
+
+	test_commit -C "$daemon_parent" two_a &&
+	git -C "$daemon_parent" rev-parse two_a >two_a_hash &&
+
+	GIT_TRACE_PACKET="$(pwd)/log" git -C daemon_child -c protocol.version=2 \
+		fetch --no-tags origin $(cat two_a_hash) &&
+
+	grep "fetch< version 2" log &&
+	! grep "fetch> command=ls-refs" log
+'
+
 test_expect_success 'pull with git:// using protocol v2' '
 	test_when_finished "rm -f log" &&
 
@@ -286,6 +299,10 @@ test_expect_success 'dynamically fetch missing object' '
 	grep "version 2" trace
 '
 
+test_expect_success 'when dynamically fetching missing object, do not list refs' '
+	! grep "git> command=ls-refs" trace
+'
+
 test_expect_success 'partial fetch' '
 	rm -rf client "$(pwd)/trace" &&
 	git init client &&

transport-helper.c

@@ -1105,6 +1105,7 @@ static struct ref *get_refs_list(struct transport *transport, int for_push,
 }
 
 static struct transport_vtable vtable = {
+	0,
 	set_helper_option,
 	get_refs_list,
 	fetch,

transport-internal.h

@@ -6,6 +6,12 @@ struct transport;
 struct argv_array;
 
 struct transport_vtable {
+	/**
+	 * This transport supports the fetch() function being called
+	 * without get_refs_list() first being called.
+	 */
+	unsigned fetch_without_list : 1;
+
 	/**
 	 * Returns 0 if successful, positive if the option is not
 	 * recognized or is inapplicable, and negative if the option

transport.c

@@ -252,8 +252,18 @@ static int connect_setup(struct transport *transport, int for_push)
 	return 0;
 }
 
-static struct ref *get_refs_via_connect(struct transport *transport, int for_push,
-					const struct argv_array *ref_prefixes)
+/*
+ * Obtains the protocol version from the transport and writes it to
+ * transport->data->version, first connecting if not already connected.
+ *
+ * If the protocol version is one that allows skipping the listing of remote
+ * refs, and must_list_refs is 0, the listing of remote refs is skipped and
+ * this function returns NULL. Otherwise, this function returns the list of
+ * remote refs.
+ */
+static struct ref *handshake(struct transport *transport, int for_push,
+			     const struct argv_array *ref_prefixes,
+			     int must_list_refs)
 {
 	struct git_transport_data *data = transport->data;
 	struct ref *refs = NULL;
@@ -268,8 +278,10 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 	data->version = discover_version(&reader);
 	switch (data->version) {
 	case protocol_v2:
+		if (must_list_refs)
 			get_remote_refs(data->fd[1], &reader, &refs, for_push,
-				ref_prefixes, transport->server_options);
+					ref_prefixes,
+					transport->server_options);
 		break;
 	case protocol_v1:
 	case protocol_v0:
@@ -283,9 +295,18 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 	}
 	data->got_remote_heads = 1;
 
+	if (reader.line_peeked)
+		BUG("buffer must be empty at the end of handshake()");
+
 	return refs;
 }
 
+static struct ref *get_refs_via_connect(struct transport *transport, int for_push,
+					const struct argv_array *ref_prefixes)
+{
+	return handshake(transport, for_push, ref_prefixes, 1);
+}
+
 static int fetch_refs_via_pack(struct transport *transport,
 			       int nr_heads, struct ref **to_fetch)
 {
@@ -320,8 +341,17 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.server_options = transport->server_options;
 	args.negotiation_tips = data->options.negotiation_tips;
 
-	if (!data->got_remote_heads)
-		refs_tmp = get_refs_via_connect(transport, 0, NULL);
+	if (!data->got_remote_heads) {
+		int i;
+		int must_list_refs = 0;
+		for (i = 0; i < nr_heads; i++) {
+			if (!to_fetch[i]->exact_oid) {
+				must_list_refs = 1;
+				break;
+			}
+		}
+		refs_tmp = handshake(transport, 0, NULL, must_list_refs);
+	}
 
 	switch (data->version) {
 	case protocol_v2:
@@ -703,6 +733,7 @@ static int disconnect_git(struct transport *transport)
 }
 
 static struct transport_vtable taken_over_vtable = {
+	1,
 	NULL,
 	get_refs_via_connect,
 	fetch_refs_via_pack,
@@ -852,6 +883,7 @@ void transport_check_allowed(const char *type)
 }
 
 static struct transport_vtable bundle_vtable = {
+	0,
 	NULL,
 	get_refs_from_bundle,
 	fetch_refs_from_bundle,
@@ -861,6 +893,7 @@ static struct transport_vtable bundle_vtable = {
 };
 
 static struct transport_vtable builtin_smart_vtable = {
+	1,
 	NULL,
 	get_refs_via_connect,
 	fetch_refs_via_pack,
@@ -1227,6 +1260,15 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs)
 	struct ref **heads = NULL;
 	struct ref *rm;
 
+	if (!transport->vtable->fetch_without_list)
+		/*
+		 * Some transports (e.g. the built-in bundle transport and the
+		 * transport helper interface) do not work when fetching is
+		 * done immediately after transport creation. List the remote
+		 * refs anyway (if not already listed) as a workaround.
+		 */
+		transport_get_remote_refs(transport, NULL);
+
 	for (rm = refs; rm; rm = rm->next) {
 		nr_refs++;
 		if (rm->peer_ref &&