[PATCH v3 1/6] fetch-pack: refactor packet writing

[Eric Ju <eric.peijian@gmail.com>]

From: Calvin Wan <calvinwan@google.com>

Refactor write_fetch_command_and_capabilities() to be a more general
purpose function write_command_and_capabilities(), so that it can be
used by both fetch and future command.

Here "command" means the "operations" supported by Git’s wire protocol
https://git-scm.com/docs/protocol-v2. An example would be a
git's subcommand, such as git-fetch(1); or an operation supported by
the server side such as "object-info" implemented in "a2ba162cda
(object-info: support for retrieving object info, 2021-04-20)".

In a future separate series, we can move
write_command_and_capabilities() to a higher-level file, such as
connect.c, so that it becomes accessible to other commands.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju  <eric.peijian@gmail.com>
---
 fetch-pack.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index f752da93a8..756fb83f89 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1314,13 +1314,14 @@ static int add_haves(struct fetch_negotiator *negotiator,
 	return haves_added;
 }
 
-static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
-						 const struct string_list *server_options)
+static void write_command_and_capabilities(struct strbuf *req_buf,
+										   const char *command,
+										   const struct string_list *server_options)
 {
 	const char *hash_name;
 
-	ensure_server_supports_v2("fetch");
-	packet_buf_write(req_buf, "command=fetch");
+	ensure_server_supports_v2(command);
+	packet_buf_write(req_buf, "command=%s", command);
 	if (server_supports_v2("agent"))
 		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
 	if (advertise_sid && server_supports_v2("session-id"))
@@ -1346,6 +1347,28 @@ static void write_fetch_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, "object-info", args->server_options);
+
+	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,
@@ -1356,7 +1379,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	int done_sent = 0;
 	struct strbuf req_buf = STRBUF_INIT;
 
-	write_fetch_command_and_capabilities(&req_buf, args->server_options);
+	write_command_and_capabilities(&req_buf, "fetch", args->server_options);
 
 	if (args->use_thin_pack)
 		packet_buf_write(&req_buf, "thin-pack");
@@ -2174,7 +2197,7 @@ void negotiate_using_fetch(const struct oid_array *negotiation_tips,
 					   the_repository, "%d",
 					   negotiation_round);
 		strbuf_reset(&req_buf);
-		write_fetch_command_and_capabilities(&req_buf, server_options);
+		write_command_and_capabilities(&req_buf, "fetch", server_options);
 
 		packet_buf_write(&req_buf, "wait-for-done");
 
-- 
2.46.0