ls-remote: send server options when using protocol v2

Teach ls-remote to optionally accept server options by specifying them
on the cmdline via '-o' or '--server-option'.  These server options are
sent to the remote end when querying for the remote end's refs using
protocol version 2.

If communicating using a protocol other than v2 the provided options are
ignored and not sent to the remote end.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-ls-remote.txt

@@ -60,6 +60,14 @@ OPTIONS
 	upload-pack only shows the symref HEAD, so it will be the only
 	one shown by ls-remote.
 
+-o <option>::
+--server-option=<option>::
+	Transmit the given string to the server when communicating using
+	protocol version 2.  The given string must not contain a NUL or LF
+	character.
+	When multiple `--server-option=<option>` are given, they are all
+	sent to the other side in the order listed on the command line.
+
 <repository>::
 	The "remote" repository to query.  This parameter can be
 	either a URL or the name of a remote (see the GIT URLS and

builtin/ls-remote.c

@@ -45,6 +45,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 	const char *uploadpack = NULL;
 	const char **pattern = NULL;
 	struct argv_array ref_prefixes = ARGV_ARRAY_INIT;
+	struct string_list server_options = STRING_LIST_INIT_DUP;
 
 	struct remote *remote;
 	struct transport *transport;
@@ -67,6 +68,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 			      2, PARSE_OPT_NOCOMPLETE),
 		OPT_BOOL(0, "symref", &show_symref_target,
 			 N_("show underlying ref in addition to the object pointed by it")),
+		OPT_STRING_LIST('o', "server-option", &server_options, N_("server-specific"), N_("option to transmit")),
 		OPT_END()
 	};
 
@@ -107,6 +109,8 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 	transport = transport_get(remote, NULL);
 	if (uploadpack != NULL)
 		transport_set_option(transport, TRANS_OPT_UPLOADPACK, uploadpack);
+	if (server_options.nr)
+		transport->server_options = &server_options;
 
 	ref = transport_get_remote_refs(transport, &ref_prefixes);
 	if (transport_disconnect(transport))

connect.c

@@ -408,7 +408,8 @@ static int process_ref_v2(const char *line, struct ref ***list)
 
 struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 			     struct ref **list, int for_push,
-			     const struct argv_array *ref_prefixes)
+			     const struct argv_array *ref_prefixes,
+			     const struct string_list *server_options)
 {
 	int i;
 	*list = NULL;
@@ -419,6 +420,12 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 	if (server_supports_v2("agent", 0))
 		packet_write_fmt(fd_out, "agent=%s", git_user_agent_sanitized());
 
+	if (server_options && server_options->nr &&
+	    server_supports_v2("server-option", 1))
+		for (i = 0; i < server_options->nr; i++)
+			packet_write_fmt(fd_out, "server-option=%s",
+					 server_options->items[i].string);
+
 	packet_delim(fd_out);
 	/* When pushing we don't want to request the peeled tags */
 	if (!for_push)

remote.h

@@ -153,6 +153,7 @@ void free_refs(struct ref *ref);
 struct oid_array;
 struct packet_reader;
 struct argv_array;
+struct string_list;
 extern struct ref **get_remote_heads(struct packet_reader *reader,
 				     struct ref **list, unsigned int flags,
 				     struct oid_array *extra_have,
@@ -161,7 +162,8 @@ extern struct ref **get_remote_heads(struct packet_reader *reader,
 /* Used for protocol v2 in order to retrieve refs from a remote */
 extern struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 				    struct ref **list, int for_push,
-				    const struct argv_array *ref_prefixes);
+				    const struct argv_array *ref_prefixes,
+				    const struct string_list *server_options);
 
 int resolve_remote_symref(struct ref *ref, struct ref *list);
 int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid);

t/t5702-protocol-v2.sh

@@ -154,6 +154,22 @@ test_expect_success 'ref advertisment is filtered with ls-remote using protocol
 	test_cmp actual expect
 '
 
+test_expect_success 'server-options are sent when using ls-remote' '
+	test_when_finished "rm -f log" &&
+
+	GIT_TRACE_PACKET="$(pwd)/log" git -c protocol.version=2 \
+		ls-remote -o hello -o world "file://$(pwd)/file_parent" master >actual &&
+
+	cat >expect <<-EOF &&
+	$(git -C file_parent rev-parse refs/heads/master)$(printf "\t")refs/heads/master
+	EOF
+
+	test_cmp actual expect &&
+	grep "server-option=hello" log &&
+	grep "server-option=world" log
+'
+
+
 test_expect_success 'clone with file:// using protocol v2' '
 	test_when_finished "rm -f log" &&
 

transport.c

@@ -218,7 +218,7 @@ static struct ref *get_refs_via_connect(struct transport *transport, int for_pus
 	switch (data->version) {
 	case protocol_v2:
 		get_remote_refs(data->fd[1], &reader, &refs, for_push,
-				ref_prefixes);
+				ref_prefixes, transport->server_options);
 		break;
 	case protocol_v1:
 	case protocol_v0:

transport.h

@@ -71,6 +71,12 @@ struct transport {
 	 */
 	const struct string_list *push_options;
 
+	/*
+	 * These strings will be passed to the remote side on each command
+	 * request, if both sides support the server-option capability.
+	 */
+	const struct string_list *server_options;
+
 	char *pack_lockfile;
 	signed verbose : 3;
 	/**