Re: [PATCH 4/6] transport: add client support for object-info

> From: Calvin Wan <calvinwan@google.com>
>
> Sometimes it is useful to get information about an object without having
> to download it completely. The server logic has already been implemented
> as “a2ba162cda (object-info: support for retrieving object info,

> 2021-04-20)”.
>
> Add client functions to communicate with the server.
>
> The client currently supports requesting a list of object ids with
> features 'size' and 'type' from a v2 server. If a server does not

> advertise either of the requested features, then the client falls back
> to making the request through 'fetch'.
>
> Signed-off-by: Calvin Wan <calvinwan@google.com>
> Signed-off-by: Eric Ju  <eric.peijian@gmail.com>
> Helped-by: Jonathan Tan <jonathantanmy@google.com>
> Helped-by: Christian Couder <chriscool@tuxfamily.org>
> ---
>  fetch-pack.c       |  24 +++++++++++
>  fetch-pack.h       |  10 +++++
>  transport-helper.c |   8 +++-
>  transport.c        | 102 ++++++++++++++++++++++++++++++++++++++++++---
>  transport.h        |  11 +++++
>  5 files changed, 148 insertions(+), 7 deletions(-)
>
> diff --git a/fetch-pack.c b/fetch-pack.c
> index da0de9c537..d533cac1d8 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -1345,6 +1345,27 @@ static void write_command_and_capabilities(struct strbuf *req_buf,
>  	packet_buf_delim(req_buf);
>  }
>
> +void send_object_info_request(int fd_out, struct object_info_args *args)
> +{
> +	struct strbuf req_buf = STRBUF_INIT;
> +
> +	write_command_and_capabilities(&req_buf, args->server_options, "object-info");
> +
> +	if (unsorted_string_list_has_string(args->object_info_options, "size"))
> +		packet_buf_write(&req_buf, "size");
> +
> +	if (args->oids) {
> +		for (size_t i = 0; i < args->oids->nr; i++)
> +			packet_buf_write(&req_buf, "oid %s", oid_to_hex(&args->oids->oid[i]));
> +	}
> +
> +	packet_buf_flush(&req_buf);
> +	if (write_in_full(fd_out, req_buf.buf, req_buf.len) < 0)
> +		die_errno(_("unable to write request to remote"));
> +
> +	strbuf_release(&req_buf);
> +}
> +
>  static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
>  			      struct fetch_pack_args *args,
>  			      const struct ref *wants, struct oidset *common,
> @@ -1682,6 +1703,9 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
>  	if (args->depth > 0 || args->deepen_since || args->deepen_not)
>  		args->deepen = 1;
>
> +	if (args->object_info)
> +		state = FETCH_SEND_REQUEST;
> +
>  	while (state != FETCH_DONE) {
>  		switch (state) {
>  		case FETCH_CHECK_LOCAL:
> diff --git a/fetch-pack.h b/fetch-pack.h
> index 6775d26517..16e4dc0824 100644
> --- a/fetch-pack.h
> +++ b/fetch-pack.h
> @@ -16,6 +16,7 @@ struct fetch_pack_args {
>  	const struct string_list *deepen_not;
>  	struct list_objects_filter_options filter_options;
>  	const struct string_list *server_options;
> +	struct object_info **object_info_data;
>
>  	/*
>  	 * If not NULL, during packfile negotiation, fetch-pack will send "have"
> @@ -42,6 +43,7 @@ struct fetch_pack_args {
>  	unsigned reject_shallow_remote:1;
>  	unsigned deepen:1;
>  	unsigned refetch:1;
> +	unsigned object_info:1;
>
>  	/*
>  	 * Indicate that the remote of this request is a promisor remote. The
> @@ -68,6 +70,12 @@ struct fetch_pack_args {
>  	unsigned connectivity_checked:1;
>  };
>
> +struct object_info_args {
> +	struct string_list *object_info_options;
> +	const struct string_list *server_options;
> +	struct oid_array *oids;
> +};
> +
>  /*
>   * sought represents remote references that should be updated from.
>   * On return, the names that were found on the remote will have been
> @@ -101,4 +109,6 @@ void negotiate_using_fetch(const struct oid_array *negotiation_tips,
>   */
>  int report_unmatched_refs(struct ref **sought, int nr_sought);
>
> +void send_object_info_request(int fd_out, struct object_info_args *args);
> +
>  #endif
> diff --git a/transport-helper.c b/transport-helper.c
> index 9820947ab2..670d1e7068 100644
> --- a/transport-helper.c
> +++ b/transport-helper.c
> @@ -697,13 +697,17 @@ static int fetch_refs(struct transport *transport,
>
>  	/*
>  	 * If we reach here, then the server, the client, and/or the transport
> -	 * helper does not support protocol v2. --negotiate-only requires
> -	 * protocol v2.
> +	 * helper does not support protocol v2. --negotiate-only and cat-file remote-object-info
> +	 * require protocol v2.
>  	 */
>  	if (data->transport_options.acked_commits) {
>  		warning(_("--negotiate-only requires protocol v2"));
>  		return -1;
>  	}
> +	if (transport->smart_options->object_info) {
> +		// fail the command explicitly to avoid further commands input
> +		die(_("remote-object-info requires protocol v2"));
> +	}
>
>  	if (!data->get_refs_list_called)
>  		get_refs_list_using_list(transport, 0);
> diff --git a/transport.c b/transport.c
> index 83ddea8fbc..2847aa3f3c 100644
> --- a/transport.c
> +++ b/transport.c
> @@ -363,6 +363,73 @@ static struct ref *handshake(struct transport *transport, int for_push,
>  	return refs;
>  }
>
> +static int fetch_object_info(struct transport *transport, struct object_info **object_info_data)
> +{
> +	int size_index = -1;
> +	struct git_transport_data *data = transport->data;
> +	struct object_info_args args;
> +	struct packet_reader reader;
> +
> +	memset(&args, 0, sizeof(args));

> +	args.server_options = transport->server_options;
> +	args.object_info_options = transport->smart_options->object_info_options;
> +	args.oids = transport->smart_options->object_info_oids;
> +
> +	connect_setup(transport, 0);
> +	packet_reader_init(&reader, data->fd[0], NULL, 0,
> +			PACKET_READ_CHOMP_NEWLINE |
> +			PACKET_READ_GENTLE_ON_EOF |
> +			PACKET_READ_DIE_ON_ERR_PACKET);
> +	data->version = discover_version(&reader);
> +
> +	transport->hash_algo = reader.hash_algo;
> +
> +	switch (data->version) {
> +	case protocol_v2:
> +		if (!server_supports_v2("object-info"))
> +			return -1;
> +		if (unsorted_string_list_has_string(args.object_info_options, "size")
> +				&& !server_supports_feature("object-info", "size", 0)) {
> +			return -1;
> +		}
> +		send_object_info_request(data->fd[1], &args);
> +		break;
> +	case protocol_v1:
> +	case protocol_v0:
> +		die(_("wrong protocol version. expected v2"));
> +	case protocol_unknown_version:
> +		BUG("unknown protocol version");
> +	}
> +
> +	for (size_t i = 0; i < args.object_info_options->nr; i++) {
> +		if (packet_reader_read(&reader) != PACKET_READ_NORMAL) {
> +			check_stateless_delimiter(transport->stateless_rpc, &reader, "stateless delimiter expected");
> +			return -1;
> +		}
> +		if (unsorted_string_list_has_string(args.object_info_options, reader.line)) {
> +			if (!strcmp(reader.line, "size"))
> +				size_index = i;
> +			continue;
> +		}
> +		return -1;
> +	}
> +
> +	for (size_t i = 0; packet_reader_read(&reader) == PACKET_READ_NORMAL && i < args.oids->nr; i++){
> +		struct string_list object_info_values = STRING_LIST_INIT_DUP;

> +
> +		string_list_split(&object_info_values, reader.line, ' ', -1);
> +		if (0 <= size_index) {
> +			if (!strcmp(object_info_values.items[1 + size_index].string, ""))
> +				die("object-info: not our ref %s",
> +					object_info_values.items[0].string);
> +			*(*object_info_data)[i].sizep = strtoul(object_info_values.items[1 + size_index].string, NULL, 10);

> +		}
> +	}
> +	check_stateless_delimiter(transport->stateless_rpc, &reader, "stateless delimiter expected");
> +
> +	return 0;
> +}
> +
>  static struct ref *get_refs_via_connect(struct transport *transport, int for_push,
>  					struct transport_ls_refs_options *options)
>  {
> @@ -410,6 +477,7 @@ static int fetch_refs_via_pack(struct transport *transport,
>  	struct ref *refs = NULL;
>  	struct fetch_pack_args args;
>  	struct ref *refs_tmp = NULL;
> +	struct ref *object_info_refs = xcalloc(1, sizeof (struct ref));
>
>  	memset(&args, 0, sizeof(args));
>  	args.uploadpack = data->options.uploadpack;
> @@ -436,11 +504,27 @@ static int fetch_refs_via_pack(struct transport *transport,
>  	args.server_options = transport->server_options;
>  	args.negotiation_tips = data->options.negotiation_tips;
>  	args.reject_shallow_remote = transport->smart_options->reject_shallow;
> -
> -	if (!data->finished_handshake) {
> -		int i;
> +	args.object_info = transport->smart_options->object_info;
> +
> +	if (transport->smart_options && transport->smart_options->object_info) {
> +		struct ref *ref = object_info_refs;
> +
> +		if (!fetch_object_info(transport, data->options.object_info_data))
> +			goto cleanup;
> +		args.object_info_data = data->options.object_info_data;
> +		args.quiet = 1;
> +		args.no_progress = 1;
> +		for (size_t i = 0; i < transport->smart_options->object_info_oids->nr; i++) {
> +			struct ref *temp_ref = xcalloc(1, sizeof (struct ref));
> +			temp_ref->old_oid = *(transport->smart_options->object_info_oids->oid + i);
> +			temp_ref->exact_oid = 1;
> +			ref->next = temp_ref;
> +			ref = ref->next;
> +		}
> +		transport->remote_refs = object_info_refs->next;
> +	} else if (!data->finished_handshake) {
>  		int must_list_refs = 0;
> -		for (i = 0; i < nr_heads; i++) {
> +		for (int i = 0; i < nr_heads; i++) {
>  			if (!to_fetch[i]->exact_oid) {
>  				must_list_refs = 1;
>  				break;
> @@ -478,11 +562,18 @@ static int fetch_refs_via_pack(struct transport *transport,
>  			  &transport->pack_lockfiles, data->version);
>
>  	data->finished_handshake = 0;
> +	if (args.object_info) {
> +		struct ref *ref_cpy_reader = object_info_refs->next;
> +		for (int i = 0; ref_cpy_reader; i++) {
> +			oid_object_info_extended(the_repository, &ref_cpy_reader->old_oid, &(*args.object_info_data)[i], OBJECT_INFO_LOOKUP_REPLACE);
> +			ref_cpy_reader = ref_cpy_reader->next;
> +		}
> +	}
>  	data->options.self_contained_and_connected =
>  		args.self_contained_and_connected;
>  	data->options.connectivity_checked = args.connectivity_checked;
>
> -	if (!refs)
> +	if (!refs && !args.object_info)
>  		ret = -1;
>  	if (report_unmatched_refs(to_fetch, nr_heads))
>  		ret = -1;
> @@ -498,6 +589,7 @@ static int fetch_refs_via_pack(struct transport *transport,
>  	free_refs(refs_tmp);
>  	free_refs(refs);
>  	list_objects_filter_release(&args.filter_options);
> +	free_refs(object_info_refs);

>  	return ret;
>  }
>
> diff --git a/transport.h b/transport.h
> index 6393cd9823..5a3cda1860 100644
> --- a/transport.h
> +++ b/transport.h
> @@ -5,6 +5,7 @@
>  #include "remote.h"
>  #include "list-objects-filter-options.h"
>  #include "string-list.h"
> +#include "object-store.h"
>
>  struct git_transport_options {
>  	unsigned thin : 1;
> @@ -30,6 +31,12 @@ struct git_transport_options {
>  	 */
>  	unsigned connectivity_checked:1;
>
> +	/*
> +	 * Transport will attempt to pull only object-info. Fallbacks
> +	 * to pulling entire object if object-info is not supported.
> +	 */
> +	unsigned object_info : 1;
> +
>  	int depth;
>  	const char *deepen_since;
>  	const struct string_list *deepen_not;
> @@ -53,6 +60,10 @@ struct git_transport_options {
>  	 * common commits to this oidset instead of fetching any packfiles.
>  	 */
>  	struct oidset *acked_commits;
> +
> +	struct oid_array *object_info_oids;
> +	struct object_info **object_info_data;
> +	struct string_list *object_info_options;
>  };
>
>  enum transport_family {
> --
> 2.45.2