[RFC PATCH v2 30/36] connect: implement get_recommended_features()

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

From: Derrick Stolee <derrickstolee@github.com>

This method allows a client to request and parse the 'features' capability
of protocol v2. The response is expected to be a list of 'key=value'
lines, but this implementation does no checking of the lines, expecting
a later parse of the lines to be careful of the existence of that '='
character.

This change is based on an earlier patch [1] written for a similar
capability.

[1] https://lore.kernel.org/git/RFC-patch-04.13-21caf01775-20210805T150534Z-avarab@gmail.com/

Co-authored-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 connect.c | 36 ++++++++++++++++++++++++++++++++++++
 remote.h  |  4 ++++
 2 files changed, 40 insertions(+)

diff --git a/connect.c b/connect.c
index a8fdb5255f7..1739d1f8a5f 100644
--- a/connect.c
+++ b/connect.c
@@ -591,6 +591,42 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 	return list;
 }
 
+int get_recommended_features(int fd_out, struct packet_reader *reader,
+			     struct string_list *list, int stateless_rpc)
+{
+	int line_nr = 1;
+
+	server_supports_v2("features", 1);
+
+	/* (Re-)send capabilities */
+	send_capabilities(fd_out, reader);
+
+	/* Send command */
+	packet_write_fmt(fd_out, "command=features\n");
+	packet_delim(fd_out);
+	packet_flush(fd_out);
+
+	/* Process response from server */
+	while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
+		const char *line = reader->line;
+		line_nr++;
+
+		string_list_append(list, line);
+	}
+
+	if (reader->status != PACKET_READ_FLUSH)
+		return error(_("expected flush after features listing"));
+
+	/*
+	 * Might die(), but obscure enough that that's OK, e.g. in
+	 * serve.c, we'll call BUG() on its equivalent (the
+	 * PACKET_READ_RESPONSE_END check).
+	 */
+	check_stateless_delimiter(stateless_rpc, reader,
+		_("expected response end packet after features listing"));
+	return 0;
+}
+
 const char *parse_feature_value(const char *feature_list, const char *feature, int *lenp, int *offset)
 {
 	int len;
diff --git a/remote.h b/remote.h
index 571338510a8..bccb8484dbd 100644
--- a/remote.h
+++ b/remote.h
@@ -242,6 +242,10 @@ int get_remote_bundle_uri(int fd_out, struct packet_reader *reader,
 
 int resolve_remote_symref(struct ref *ref, struct ref *list);
 
+/* Used for protocol v2 in order to retrieve recommended features */
+int get_recommended_features(int fd_out, struct packet_reader *reader,
+			     struct string_list *list, int stateless_rpc);
+
 /*
  * Remove and free all but the first of any entries in the input list
  * that map the same remote reference to the same local reference.  If
-- 
2.36.0.rc2.902.g60576bbc845