static void add_wants(int no_dependents, const struct ref *wants, struct strbuf *req_buf)
{
	int use_ref_in_want = server_supports_feature("fetch", "ref-in-want", 0);

	for ( ; wants ; wants = wants->next) {
		const struct object_id *remote = &wants->old_oid;
		struct object *o;

		/*
		 * If that object is complete (i.e. it is an ancestor of a
		 * local ref), we tell them we have it but do not have to
		 * tell them about its ancestors, which they already know
		 * about.
		 *
		 * We use lookup_object here because we are only
		 * interested in the case we *know* the object is
		 * reachable and we have already scanned it.
		 *
		 * Do this only if args->no_dependents is false (if it is true,
		 * we cannot trust the object flags).
		 */
		if (!no_dependents &&
		    ((o = lookup_object(the_repository, remote->hash)) != NULL) &&
		    (o->flags & COMPLETE)) {
			continue;
		}

		if (!use_ref_in_want || wants->exact_oid)
			packet_buf_write(req_buf, "want %s\n", oid_to_hex(remote));
		else
			packet_buf_write(req_buf, "want-ref %s\n", wants->name);
	}
}

static int add_haves(struct fetch_negotiator *negotiator,
		     struct strbuf *req_buf,
		     int *haves_to_send, int *in_vain)
{
	int ret = 0;
	int haves_added = 0;
	const struct object_id *oid;

	while ((oid = negotiator->next(negotiator))) {
		packet_buf_write(req_buf, "have %s\n", oid_to_hex(oid));
		if (++haves_added >= *haves_to_send)
			break;
	}

	*in_vain += haves_added;
	if (!haves_added || *in_vain >= MAX_IN_VAIN) {
		/* Send Done */
		packet_buf_write(req_buf, "done\n");
		ret = 1;
	}

	/* Increase haves to send on next round */
	*haves_to_send = next_flush(1, *haves_to_send);

	return ret;
}

static int generate_push_cert(struct strbuf *req_buf,
			      const struct ref *remote_refs,
			      struct send_pack_args *args,
			      const char *cap_string,
			      const char *push_cert_nonce)
{
	const struct ref *ref;
	struct string_list_item *item;
	char *signing_key = xstrdup(get_signing_key());
	const char *cp, *np;
	struct strbuf cert = STRBUF_INIT;
	int update_seen = 0;

	strbuf_addstr(&cert, "certificate version 0.1\n");
	strbuf_addf(&cert, "pusher %s ", signing_key);
	datestamp(&cert);
	strbuf_addch(&cert, '\n');
	if (args->url && *args->url) {
		char *anon_url = transport_anonymize_url(args->url);
		strbuf_addf(&cert, "pushee %s\n", anon_url);
		free(anon_url);
	}
	if (push_cert_nonce[0])
		strbuf_addf(&cert, "nonce %s\n", push_cert_nonce);
	if (args->push_options)
		for_each_string_list_item(item, args->push_options)
			strbuf_addf(&cert, "push-option %s\n", item->string);
	strbuf_addstr(&cert, "\n");

	for (ref = remote_refs; ref; ref = ref->next) {
		if (check_to_send_update(ref, args) < 0)
			continue;
		update_seen = 1;
		strbuf_addf(&cert, "%s %s %s\n",
			    oid_to_hex(&ref->old_oid),
			    oid_to_hex(&ref->new_oid),
			    ref->name);
	}
	if (!update_seen)
		goto free_return;

	if (sign_buffer(&cert, &cert, signing_key))
		die(_("failed to sign the push certificate"));

	packet_buf_write(req_buf, "push-cert%c%s", 0, cap_string);
	for (cp = cert.buf; cp < cert.buf + cert.len; cp = np) {
		np = next_line(cp, cert.buf + cert.len - cp);
		packet_buf_write(req_buf,
				 "%.*s", (int)(np - cp), cp);
	}
	packet_buf_write(req_buf, "push-cert-end\n");

free_return:
	free(signing_key);
	strbuf_release(&cert);
	return update_seen;
}

static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
{
	struct strbuf *sb = cb;
	if (graft->nr_parent == -1)
		packet_buf_write(sb, "shallow %s\n", oid_to_hex(&graft->oid));
	return 0;
}

static void add_wants(const struct ref *wants, struct strbuf *req_buf)
{
	for ( ; wants ; wants = wants->next) {
		const struct object_id *remote = &wants->old_oid;
		const char *remote_hex;
		struct object *o;

		/*
		 * If that object is complete (i.e. it is an ancestor of a
		 * local ref), we tell them we have it but do not have to
		 * tell them about its ancestors, which they already know
		 * about.
		 *
		 * We use lookup_object here because we are only
		 * interested in the case we *know* the object is
		 * reachable and we have already scanned it.
		 */
		if (((o = lookup_object(remote->hash)) != NULL) &&
		    (o->flags & COMPLETE)) {
			continue;
		}

		remote_hex = oid_to_hex(remote);
		packet_buf_write(req_buf, "want %s\n", remote_hex);
	}
}

static int fetch_git(struct discovery *heads,
	int nr_heads, struct ref **to_fetch)
{
	struct rpc_state rpc;
	struct strbuf preamble = STRBUF_INIT;
	char *depth_arg = NULL;
	int argc = 0, i, err;
	const char *argv[16];

	argv[argc++] = "fetch-pack";
	argv[argc++] = "--stateless-rpc";
	argv[argc++] = "--stdin";
	argv[argc++] = "--lock-pack";
	if (options.followtags)
		argv[argc++] = "--include-tag";
	if (options.thin)
		argv[argc++] = "--thin";
	if (options.verbosity >= 3) {
		argv[argc++] = "-v";
		argv[argc++] = "-v";
	}
	if (options.check_self_contained_and_connected)
		argv[argc++] = "--check-self-contained-and-connected";
	if (!options.progress)
		argv[argc++] = "--no-progress";
	if (options.depth) {
		struct strbuf buf = STRBUF_INIT;
		strbuf_addf(&buf, "--depth=%lu", options.depth);
		depth_arg = strbuf_detach(&buf, NULL);
		argv[argc++] = depth_arg;
	}
	argv[argc++] = url.buf;
	argv[argc++] = NULL;

	for (i = 0; i < nr_heads; i++) {
		struct ref *ref = to_fetch[i];
		if (!ref->name || !*ref->name)
			die("cannot fetch by sha1 over smart http");
		packet_buf_write(&preamble, "%s\n", ref->name);
	}
	packet_buf_flush(&preamble);

	memset(&rpc, 0, sizeof(rpc));
	rpc.service_name = "git-upload-pack",
	rpc.argv = argv;
	rpc.stdin_preamble = &preamble;
	rpc.gzip_request = 1;

	err = rpc_service(&rpc, heads);
	if (rpc.result.len)
		write_or_die(1, rpc.result.buf, rpc.result.len);
	strbuf_release(&rpc.result);
	strbuf_release(&preamble);
	free(depth_arg);
	return err;
}

static void add_shallow_requests(struct strbuf *req_buf,
				 const struct fetch_pack_args *args)
{
	if (is_repository_shallow(the_repository))
		write_shallow_commits(req_buf, 1, NULL);
	if (args->depth > 0)
		packet_buf_write(req_buf, "deepen %d", args->depth);
	if (args->deepen_since) {
		timestamp_t max_age = approxidate(args->deepen_since);
		packet_buf_write(req_buf, "deepen-since %"PRItime, max_age);
	}
	if (args->deepen_not) {
		int i;
		for (i = 0; i < args->deepen_not->nr; i++) {
			struct string_list_item *s = args->deepen_not->items + i;
			packet_buf_write(req_buf, "deepen-not %s", s->string);
		}
	}
}

static void add_common(struct strbuf *req_buf, struct oidset *common)
{
	struct oidset_iter iter;
	const struct object_id *oid;
	oidset_iter_init(common, &iter);

	while ((oid = oidset_iter_next(&iter))) {
		packet_buf_write(req_buf, "have %s\n", oid_to_hex(oid));
	}
}

static int write_one_shallow(const struct commit_graft *graft, void *cb_data)
{
	struct write_shallow_data *data = cb_data;
	const char *hex = sha1_to_hex(graft->sha1);
	data->count++;
	if (data->use_pack_protocol)
		packet_buf_write(data->out, "shallow %s", hex);
	else {
		strbuf_addstr(data->out, hex);
		strbuf_addch(data->out, '\n');
	}
	return 0;
}

static int send_acks(struct oid_array *acks, struct strbuf *response)
{
	int i;

	packet_buf_write(response, "acknowledgments\n");

	/* Send Acks */
	if (!acks->nr)
		packet_buf_write(response, "NAK\n");

	for (i = 0; i < acks->nr; i++) {
		packet_buf_write(response, "ACK %s\n",
				 oid_to_hex(&acks->oid[i]));
	}

	if (ok_to_give_up()) {
		/* Send Ready */
		packet_buf_write(response, "ready\n");
		return 1;
	}

	return 0;
}

static int push_git(struct discovery *heads, int nr_spec, char **specs)
{
	struct rpc_state rpc;
	int i, err;
	struct argv_array args;
	struct string_list_item *cas_option;
	struct strbuf preamble = STRBUF_INIT;

	argv_array_init(&args);
	argv_array_pushl(&args, "send-pack", "--stateless-rpc", "--helper-status",
			 NULL);

	if (options.thin)
		argv_array_push(&args, "--thin");
	if (options.dry_run)
		argv_array_push(&args, "--dry-run");
	if (options.push_cert == SEND_PACK_PUSH_CERT_ALWAYS)
		argv_array_push(&args, "--signed=yes");
	else if (options.push_cert == SEND_PACK_PUSH_CERT_IF_ASKED)
		argv_array_push(&args, "--signed=if-asked");
	if (options.verbosity == 0)
		argv_array_push(&args, "--quiet");
	else if (options.verbosity > 1)
		argv_array_push(&args, "--verbose");
	for (i = 0; i < options.push_options.nr; i++)
		argv_array_pushf(&args, "--push-option=%s",
				 options.push_options.items[i].string);
	argv_array_push(&args, options.progress ? "--progress" : "--no-progress");
	for_each_string_list_item(cas_option, &cas_options)
		argv_array_push(&args, cas_option->string);
	argv_array_push(&args, url.buf);

	argv_array_push(&args, "--stdin");
	for (i = 0; i < nr_spec; i++)
		packet_buf_write(&preamble, "%s\n", specs[i]);
	packet_buf_flush(&preamble);

	memset(&rpc, 0, sizeof(rpc));
	rpc.service_name = "git-receive-pack",
	rpc.argv = args.argv;
	rpc.stdin_preamble = &preamble;

	err = rpc_service(&rpc, heads);
	if (rpc.result.len)
		write_or_die(1, rpc.result.buf, rpc.result.len);
	strbuf_release(&rpc.result);
	strbuf_release(&preamble);
	argv_array_clear(&args);
	return err;
}

static void report(struct command *commands, const char *unpack_status)
{
	struct command *cmd;
	struct strbuf buf = STRBUF_INIT;

	packet_buf_write(&buf, "unpack %s\n",
			 unpack_status ? unpack_status : "ok");
	for (cmd = commands; cmd; cmd = cmd->next) {
		if (!cmd->error_string)
			packet_buf_write(&buf, "ok %s\n",
					 cmd->ref_name);
		else
			packet_buf_write(&buf, "ng %s %s\n",
					 cmd->ref_name, cmd->error_string);
	}
	packet_buf_flush(&buf);

	if (use_sideband)
		send_sideband(1, 1, buf.buf, buf.len, use_sideband);
	else
		safe_write(1, buf.buf, buf.len);
	strbuf_release(&buf);
}

static int send_fetch_request(int fd_out, const struct fetch_pack_args *args,
			      const struct ref *wants, struct oidset *common,
			      int *haves_to_send, int *in_vain)
{
	int ret = 0;
	struct strbuf req_buf = STRBUF_INIT;

	if (server_supports_v2("fetch", 1))
		packet_buf_write(&req_buf, "command=fetch");
	if (server_supports_v2("agent", 0))
		packet_buf_write(&req_buf, "agent=%s", git_user_agent_sanitized());

	packet_buf_delim(&req_buf);
	if (args->use_thin_pack)
		packet_buf_write(&req_buf, "thin-pack");
	if (args->no_progress)
		packet_buf_write(&req_buf, "no-progress");
	if (args->include_tag)
		packet_buf_write(&req_buf, "include-tag");
	if (prefer_ofs_delta)
		packet_buf_write(&req_buf, "ofs-delta");

	/* Add shallow-info and deepen request */
	if (server_supports_feature("fetch", "shallow", 0))
		add_shallow_requests(&req_buf, args);
	else if (is_repository_shallow() || args->deepen)
		die(_("Server does not support shallow requests"));

	/* add wants */
	add_wants(wants, &req_buf);

	/* Add all of the common commits we've found in previous rounds */
	add_common(&req_buf, common);

	/* Add initial haves */
	ret = add_haves(&req_buf, haves_to_send, in_vain);

	/* Send request */
	packet_buf_flush(&req_buf);
	write_or_die(fd_out, req_buf.buf, req_buf.len);

	strbuf_release(&req_buf);
	return ret;
}

static int find_common(struct fetch_pack_args *args,
		       int fd[2], unsigned char *result_sha1,
		       struct ref *refs)
{
	int fetching;
	int count = 0, flushes = 0, flush_at = INITIAL_FLUSH, retval;
	const unsigned char *sha1;
	unsigned in_vain = 0;
	int got_continue = 0;
	int got_ready = 0;
	struct strbuf req_buf = STRBUF_INIT;
	size_t state_len = 0;

	if (args->stateless_rpc && multi_ack == 1)
		die("--stateless-rpc requires multi_ack_detailed");
	if (marked)
		for_each_ref(clear_marks, NULL);
	marked = 1;

	for_each_ref(rev_list_insert_ref, NULL);
	for_each_alternate_ref(insert_one_alternate_ref, NULL);

	fetching = 0;
	for ( ; refs ; refs = refs->next) {
		unsigned char *remote = refs->old_sha1;
		const char *remote_hex;
		struct object *o;

		/*
		 * If that object is complete (i.e. it is an ancestor of a
		 * local ref), we tell them we have it but do not have to
		 * tell them about its ancestors, which they already know
		 * about.
		 *
		 * We use lookup_object here because we are only
		 * interested in the case we *know* the object is
		 * reachable and we have already scanned it.
		 */
		if (((o = lookup_object(remote)) != NULL) &&
				(o->flags & COMPLETE)) {
			continue;
		}

		remote_hex = sha1_to_hex(remote);
		if (!fetching) {
			struct strbuf c = STRBUF_INIT;
			if (multi_ack == 2)     strbuf_addstr(&c, " multi_ack_detailed");
			if (multi_ack == 1)     strbuf_addstr(&c, " multi_ack");
			if (no_done)            strbuf_addstr(&c, " no-done");
			if (use_sideband == 2)  strbuf_addstr(&c, " side-band-64k");
			if (use_sideband == 1)  strbuf_addstr(&c, " side-band");
			if (args->use_thin_pack) strbuf_addstr(&c, " thin-pack");
			if (args->no_progress)   strbuf_addstr(&c, " no-progress");
			if (args->include_tag)   strbuf_addstr(&c, " include-tag");
			if (prefer_ofs_delta)   strbuf_addstr(&c, " ofs-delta");
			if (agent_supported)    strbuf_addf(&c, " agent=%s",
							    git_user_agent_sanitized());
			packet_buf_write(&req_buf, "want %s%s\n", remote_hex, c.buf);
			strbuf_release(&c);
		} else
			packet_buf_write(&req_buf, "want %s\n", remote_hex);
		fetching++;
	}

	if (!fetching) {
		strbuf_release(&req_buf);
		packet_flush(fd[1]);
		return 1;
	}

	if (is_repository_shallow())
		write_shallow_commits(&req_buf, 1, NULL);
	if (args->depth > 0)
		packet_buf_write(&req_buf, "deepen %d", args->depth);
	packet_buf_flush(&req_buf);
	state_len = req_buf.len;

	if (args->depth > 0) {
		char *line;
		const char *arg;
		unsigned char sha1[20];

		send_request(args, fd[1], &req_buf);
		while ((line = packet_read_line(fd[0], NULL))) {
			if (skip_prefix(line, "shallow ", &arg)) {
				if (get_sha1_hex(arg, sha1))
					die("invalid shallow line: %s", line);
				register_shallow(sha1);
				continue;
			}
			if (skip_prefix(line, "unshallow ", &arg)) {
				if (get_sha1_hex(arg, sha1))
					die("invalid unshallow line: %s", line);
				if (!lookup_object(sha1))
					die("object not found: %s", line);
				/* make sure that it is parsed as shallow */
				if (!parse_object(sha1))
					die("error in object: %s", line);
				if (unregister_shallow(sha1))
					die("no shallow found: %s", line);
//.........这里部分代码省略.........

int transport_update_ref_remote(struct transport* transport,
				struct ref *remote_refs) {
	// On this command, we need to reproduce small parts of other commands,
	// but because we want to avoid the assumption that we are running from
	// a local git repository, we'll not re-use that code.
	struct git_transport_data *data = transport->data;
	int ret = 0;
	if (!data->got_remote_heads) {
		struct ref *tmp_refs;
		connect_setup(transport, 1, 0);
		get_remote_heads(data->fd[0], NULL, 0, &tmp_refs, REF_NORMAL,
				 NULL, &data->shallow);
		data->got_remote_heads = 1;
	}
	

	// Now we skip into the functionality from send_pack, where
	// we send the new refs to the server. Since this is a lower-level
	// command, we do not do all the checks from
	// set_ref_status_for_push. We also do support all the options
	// that send_pack does
	//
	// TODO: support omitting the old value for existing refs
	struct strbuf req_buf = STRBUF_INIT;
	struct ref *ref;
	int out = data->fd[1];
	for (ref = remote_refs; ref; ref = ref->next) {
	  char *old_hex = sha1_to_hex(ref->old_sha1);
	  char *new_hex = sha1_to_hex(ref->new_sha1);
	  packet_buf_write(&req_buf, "%s %s %s",
			     old_hex, new_hex, ref->name);
	}
	write_or_die(out, req_buf.buf, req_buf.len);
	packet_flush(out);
	strbuf_release(&req_buf);

	// And finally, we skip all the way to write_pack_file
	// This is actually the part that would absolutely depend on
	// having a local git repository.
	//
	// The basic assumption here is that you can only use this
	// command for objects that are already in the remote,
	// otherwise this would be a regular push.
	//
	// The end result is that the pack we need to send is always
	// empty.
	struct sha1file *f;
	unsigned char sha1[20];
	f = sha1fd_throughput(out, "<stdout>", NULL);
	write_pack_header(f, 0);
	sha1close(f, sha1, CSUM_CLOSE);

	// We now finish the connection on the same fashion that
	// git_transport_push does
	close(data->fd[1]);
	close(data->fd[0]);
	ret |= finish_connect(data->conn);
	data->conn = NULL;
	data->got_remote_heads = 0;

	return ret;
}				    

int send_pack(struct send_pack_args *args,
	      int fd[], struct child_process *conn,
	      struct ref *remote_refs,
	      struct extra_have_objects *extra_have)
{
	int in = fd[0];
	int out = fd[1];
	struct strbuf req_buf = STRBUF_INIT;
	struct ref *ref;
	int new_refs;
	int allow_deleting_refs = 0;
	int status_report = 0;
	int use_sideband = 0;
	unsigned cmds_sent = 0;
	int ret;
	struct async demux;

	/* Does the other end support the reporting? */
	if (server_supports("report-status"))
		status_report = 1;
	if (server_supports("delete-refs"))
		allow_deleting_refs = 1;
	if (server_supports("ofs-delta"))
		args->use_ofs_delta = 1;
	if (server_supports("side-band-64k"))
		use_sideband = 1;

	if (!remote_refs) {
		fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
			"Perhaps you should specify a branch such as 'master'.\n");
		return 0;
	}

	/*
	 * Finally, tell the other end!
	 */
	new_refs = 0;
	for (ref = remote_refs; ref; ref = ref->next) {
		if (!ref->peer_ref && !args->send_mirror)
			continue;

		/* Check for statuses set by set_ref_status_for_push() */
		switch (ref->status) {
		case REF_STATUS_REJECT_NONFASTFORWARD:
		case REF_STATUS_UPTODATE:
			continue;
		default:
			; /* do nothing */
		}

		if (ref->deletion && !allow_deleting_refs) {
			ref->status = REF_STATUS_REJECT_NODELETE;
			continue;
		}

		if (!ref->deletion)
			new_refs++;

		if (args->dry_run) {
			ref->status = REF_STATUS_OK;
		} else {
			char *old_hex = sha1_to_hex(ref->old_sha1);
			char *new_hex = sha1_to_hex(ref->new_sha1);

			if (!cmds_sent && (status_report || use_sideband)) {
				packet_buf_write(&req_buf, "%s %s %s%c%s%s",
					old_hex, new_hex, ref->name, 0,
					status_report ? " report-status" : "",
					use_sideband ? " side-band-64k" : "");
			}
			else
				packet_buf_write(&req_buf, "%s %s %s",
					old_hex, new_hex, ref->name);
			ref->status = status_report ?
				REF_STATUS_EXPECTING_REPORT :
				REF_STATUS_OK;
			cmds_sent++;
		}
	}

	if (args->stateless_rpc) {
		if (!args->dry_run && cmds_sent) {
			packet_buf_flush(&req_buf);
			send_sideband(out, -1, req_buf.buf, req_buf.len, LARGE_PACKET_MAX);
		}
	} else {
		safe_write(out, req_buf.buf, req_buf.len);
		packet_flush(out);
	}
	strbuf_release(&req_buf);

	if (use_sideband && cmds_sent) {
		memset(&demux, 0, sizeof(demux));
		demux.proc = sideband_demux;
		demux.data = fd;
		demux.out = -1;
		if (start_async(&demux))
			die("send-pack: unable to fork off sideband demultiplexer");
		in = demux.out;
	}
//.........这里部分代码省略.........

static int find_common(struct fetch_negotiator *negotiator,
		       struct fetch_pack_args *args,
		       int fd[2], struct object_id *result_oid,
		       struct ref *refs)
{
	int fetching;
	int count = 0, flushes = 0, flush_at = INITIAL_FLUSH, retval;
	const struct object_id *oid;
	unsigned in_vain = 0;
	int got_continue = 0;
	int got_ready = 0;
	struct strbuf req_buf = STRBUF_INIT;
	size_t state_len = 0;

	if (args->stateless_rpc && multi_ack == 1)
		die(_("--stateless-rpc requires multi_ack_detailed"));

	if (!args->no_dependents) {
		mark_tips(negotiator, args->negotiation_tips);
		for_each_cached_alternate(negotiator, insert_one_alternate_object);
	}

	fetching = 0;
	for ( ; refs ; refs = refs->next) {
		struct object_id *remote = &refs->old_oid;
		const char *remote_hex;
		struct object *o;

		/*
		 * If that object is complete (i.e. it is an ancestor of a
		 * local ref), we tell them we have it but do not have to
		 * tell them about its ancestors, which they already know
		 * about.
		 *
		 * We use lookup_object here because we are only
		 * interested in the case we *know* the object is
		 * reachable and we have already scanned it.
		 *
		 * Do this only if args->no_dependents is false (if it is true,
		 * we cannot trust the object flags).
		 */
		if (!args->no_dependents &&
		    ((o = lookup_object(the_repository, remote->hash)) != NULL) &&
				(o->flags & COMPLETE)) {
			continue;
		}

		remote_hex = oid_to_hex(remote);
		if (!fetching) {
			struct strbuf c = STRBUF_INIT;
			if (multi_ack == 2)     strbuf_addstr(&c, " multi_ack_detailed");
			if (multi_ack == 1)     strbuf_addstr(&c, " multi_ack");
			if (no_done)            strbuf_addstr(&c, " no-done");
			if (use_sideband == 2)  strbuf_addstr(&c, " side-band-64k");
			if (use_sideband == 1)  strbuf_addstr(&c, " side-band");
			if (args->deepen_relative) strbuf_addstr(&c, " deepen-relative");
			if (args->use_thin_pack) strbuf_addstr(&c, " thin-pack");
			if (args->no_progress)   strbuf_addstr(&c, " no-progress");
			if (args->include_tag)   strbuf_addstr(&c, " include-tag");
			if (prefer_ofs_delta)   strbuf_addstr(&c, " ofs-delta");
			if (deepen_since_ok)    strbuf_addstr(&c, " deepen-since");
			if (deepen_not_ok)      strbuf_addstr(&c, " deepen-not");
			if (agent_supported)    strbuf_addf(&c, " agent=%s",
							    git_user_agent_sanitized());
			if (args->filter_options.choice)
				strbuf_addstr(&c, " filter");
			packet_buf_write(&req_buf, "want %s%s\n", remote_hex, c.buf);
			strbuf_release(&c);
		} else
			packet_buf_write(&req_buf, "want %s\n", remote_hex);
		fetching++;
	}

	if (!fetching) {
		strbuf_release(&req_buf);
		packet_flush(fd[1]);
		return 1;
	}

	if (is_repository_shallow(the_repository))
		write_shallow_commits(&req_buf, 1, NULL);
	if (args->depth > 0)
		packet_buf_write(&req_buf, "deepen %d", args->depth);
	if (args->deepen_since) {
		timestamp_t max_age = approxidate(args->deepen_since);
		packet_buf_write(&req_buf, "deepen-since %"PRItime, max_age);
	}
	if (args->deepen_not) {
		int i;
		for (i = 0; i < args->deepen_not->nr; i++) {
			struct string_list_item *s = args->deepen_not->items + i;
			packet_buf_write(&req_buf, "deepen-not %s", s->string);
		}
	}
	if (server_supports_filtering && args->filter_options.choice)
		packet_buf_write(&req_buf, "filter %s",
				 args->filter_options.filter_spec);
	packet_buf_flush(&req_buf);
	state_len = req_buf.len;

//.........这里部分代码省略.........

static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
			      const struct fetch_pack_args *args,
			      const struct ref *wants, struct oidset *common,
			      int *haves_to_send, int *in_vain)
{
	int ret = 0;
	struct strbuf req_buf = STRBUF_INIT;

	if (server_supports_v2("fetch", 1))
		packet_buf_write(&req_buf, "command=fetch");
	if (server_supports_v2("agent", 0))
		packet_buf_write(&req_buf, "agent=%s", git_user_agent_sanitized());
	if (args->server_options && args->server_options->nr &&
	    server_supports_v2("server-option", 1)) {
		int i;
		for (i = 0; i < args->server_options->nr; i++)
			packet_write_fmt(fd_out, "server-option=%s",
					 args->server_options->items[i].string);
	}

	packet_buf_delim(&req_buf);
	if (args->use_thin_pack)
		packet_buf_write(&req_buf, "thin-pack");
	if (args->no_progress)
		packet_buf_write(&req_buf, "no-progress");
	if (args->include_tag)
		packet_buf_write(&req_buf, "include-tag");
	if (prefer_ofs_delta)
		packet_buf_write(&req_buf, "ofs-delta");

	/* Add shallow-info and deepen request */
	if (server_supports_feature("fetch", "shallow", 0))
		add_shallow_requests(&req_buf, args);
	else if (is_repository_shallow(the_repository) || args->deepen)
		die(_("Server does not support shallow requests"));

	/* Add filter */
	if (server_supports_feature("fetch", "filter", 0) &&
	    args->filter_options.choice) {
		print_verbose(args, _("Server supports filter"));
		packet_buf_write(&req_buf, "filter %s",
				 args->filter_options.filter_spec);
	} else if (args->filter_options.choice) {
		warning("filtering not recognized by server, ignoring");
	}

	/* add wants */
	add_wants(args->no_dependents, wants, &req_buf);

	if (args->no_dependents) {
		packet_buf_write(&req_buf, "done");
		ret = 1;
	} else {
		/* Add all of the common commits we've found in previous rounds */
		add_common(&req_buf, common);

		/* Add initial haves */
		ret = add_haves(negotiator, &req_buf, haves_to_send, in_vain);
	}

	/* Send request */
	packet_buf_flush(&req_buf);
	write_or_die(fd_out, req_buf.buf, req_buf.len);

	strbuf_release(&req_buf);
	return ret;
}

//.........这里部分代码省略.........
			 * we were to send it and we're trying to send the refs
			 * atomically, abort the whole operation.
			 */
			if (use_atomic)
				return atomic_push_failure(args, remote_refs, ref);
			/* Fallthrough for non atomic case. */
		default:
			continue;
		}
		if (!ref->deletion)
			need_pack_data = 1;

		if (args->dry_run || !status_report)
			ref->status = REF_STATUS_OK;
		else
			ref->status = REF_STATUS_EXPECTING_REPORT;
	}

	/*
	 * Finally, tell the other end!
	 */
	for (ref = remote_refs; ref; ref = ref->next) {
		char *old_hex, *new_hex;

		if (args->dry_run || push_cert_nonce)
			continue;

		if (check_to_send_update(ref, args) < 0)
			continue;

		old_hex = oid_to_hex(&ref->old_oid);
		new_hex = oid_to_hex(&ref->new_oid);
		if (!cmds_sent) {
			packet_buf_write(&req_buf,
					 "%s %s %s%c%s",
					 old_hex, new_hex, ref->name, 0,
					 cap_buf.buf);
			cmds_sent = 1;
		} else {
			packet_buf_write(&req_buf, "%s %s %s",
					 old_hex, new_hex, ref->name);
		}
	}

	if (args->stateless_rpc) {
		if (!args->dry_run && (cmds_sent || is_repository_shallow())) {
			packet_buf_flush(&req_buf);
			send_sideband(out, -1, req_buf.buf, req_buf.len, LARGE_PACKET_MAX);
		}
	} else {
		write_or_die(out, req_buf.buf, req_buf.len);
		packet_flush(out);
	}
	strbuf_release(&req_buf);
	strbuf_release(&cap_buf);

	if (use_push_options) {
		struct string_list_item *item;
		struct strbuf sb = STRBUF_INIT;

		for_each_string_list_item(item, args->push_options)
			packet_buf_write(&sb, "%s", item->string);

		write_or_die(out, sb.buf, sb.len);
		packet_flush(out);
		strbuf_release(&sb);

static int fetch_git(struct discovery *heads,
	int nr_heads, struct ref **to_fetch)
{
	struct rpc_state rpc;
	struct strbuf preamble = STRBUF_INIT;
	int i, err;
	struct argv_array args = ARGV_ARRAY_INIT;

	argv_array_pushl(&args, "fetch-pack", "--stateless-rpc",
			 "--stdin", "--lock-pack", NULL);
	if (options.followtags)
		argv_array_push(&args, "--include-tag");
	if (options.thin)
		argv_array_push(&args, "--thin");
	if (options.verbosity >= 3)
		argv_array_pushl(&args, "-v", "-v", NULL);
	if (options.check_self_contained_and_connected)
		argv_array_push(&args, "--check-self-contained-and-connected");
	if (options.cloning)
		argv_array_push(&args, "--cloning");
	if (options.update_shallow)
		argv_array_push(&args, "--update-shallow");
	if (!options.progress)
		argv_array_push(&args, "--no-progress");
	if (options.depth)
		argv_array_pushf(&args, "--depth=%lu", options.depth);
	if (options.deepen_since)
		argv_array_pushf(&args, "--shallow-since=%s", options.deepen_since);
	for (i = 0; i < options.deepen_not.nr; i++)
		argv_array_pushf(&args, "--shallow-exclude=%s",
				 options.deepen_not.items[i].string);
	if (options.deepen_relative && options.depth)
		argv_array_push(&args, "--deepen-relative");
	if (options.from_promisor)
		argv_array_push(&args, "--from-promisor");
	if (options.no_dependents)
		argv_array_push(&args, "--no-dependents");
	if (options.filter)
		argv_array_pushf(&args, "--filter=%s", options.filter);
	argv_array_push(&args, url.buf);

	for (i = 0; i < nr_heads; i++) {
		struct ref *ref = to_fetch[i];
		if (!*ref->name)
			die("cannot fetch by sha1 over smart http");
		packet_buf_write(&preamble, "%s %s\n",
				 oid_to_hex(&ref->old_oid), ref->name);
	}
	packet_buf_flush(&preamble);

	memset(&rpc, 0, sizeof(rpc));
	rpc.service_name = "git-upload-pack",
	rpc.argv = args.argv;
	rpc.stdin_preamble = &preamble;
	rpc.gzip_request = 1;

	err = rpc_service(&rpc, heads);
	if (rpc.result.len)
		write_or_die(1, rpc.result.buf, rpc.result.len);
	strbuf_release(&rpc.result);
	strbuf_release(&preamble);
	argv_array_clear(&args);
	return err;
}