[RFC PATCH v2 27/36] protocol-caps: implement cap_features()

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

From: Derrick Stolee <derrickstolee@github.com>

The 'features' capability sends a list of "key=value" pairs from the
server. These are a set of fixed config values, all prefixed with
"serve." to avoid conflicting with other config values of similar names.

The initial set chosen here are:

* bundleURI: Allow advertising one or more bundle servers by URI.

* partialCloneFilter: Advertise one or more recommended partial clone
  filters.

* sparseCheckout: Advertise that this repository recommends using the
  sparse-checkout feature in cone mode.

The client will have the choice to enable these features.

RFC-TODO: Create Documentation/config/serve.txt

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 protocol-caps.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++
 protocol-caps.h |  1 +
 2 files changed, 67 insertions(+)

diff --git a/protocol-caps.c b/protocol-caps.c
index bbde91810ac..88b01c4133e 100644
--- a/protocol-caps.c
+++ b/protocol-caps.c
@@ -8,6 +8,7 @@
 #include "object-store.h"
 #include "string-list.h"
 #include "strbuf.h"
+#include "config.h"
 
 struct requested_info {
 	unsigned size : 1;
@@ -111,3 +112,68 @@ int cap_object_info(struct repository *r, struct packet_reader *request)
 
 	return 0;
 }
+
+static void send_lines(struct repository *r, struct packet_writer *writer,
+		       struct string_list *str_list)
+{
+	struct string_list_item *item;
+
+	if (!str_list->nr)
+		return;
+
+	for_each_string_list_item (item, str_list) {
+		packet_writer_write(writer, "%s", item->string);
+	}
+}
+
+int cap_features(struct repository *r, struct packet_reader *request)
+{
+	struct packet_writer writer;
+	struct string_list feature_list = STRING_LIST_INIT_DUP;
+	int i = 0;
+	const char *keys[] = {
+		"bundleuri",
+		"partialclonefilter",
+		"sparsecheckout",
+		NULL
+	};
+	struct strbuf serve_feature = STRBUF_INIT;
+	struct strbuf key_equals_value = STRBUF_INIT;
+	size_t len;
+	strbuf_add(&serve_feature, "serve.", 6);
+	len = serve_feature.len;
+
+	packet_writer_init(&writer, 1);
+
+	while (keys[i]) {
+		struct string_list_item *item;
+		const struct string_list *values = NULL;
+		strbuf_setlen(&serve_feature, len);
+		strbuf_addstr(&serve_feature, keys[i]);
+
+		values = repo_config_get_value_multi(r, serve_feature.buf);
+
+		if (values) {
+			for_each_string_list_item(item, values) {
+				strbuf_reset(&key_equals_value);
+				strbuf_addstr(&key_equals_value, keys[i]);
+				strbuf_addch(&key_equals_value, '=');
+				strbuf_addstr(&key_equals_value, item->string);
+
+				string_list_append(&feature_list, key_equals_value.buf);
+			}
+		}
+
+		i++;
+	}
+	strbuf_release(&serve_feature);
+	strbuf_release(&key_equals_value);
+
+	send_lines(r, &writer, &feature_list);
+
+	string_list_clear(&feature_list, 1);
+
+	packet_flush(1);
+
+	return 0;
+}
diff --git a/protocol-caps.h b/protocol-caps.h
index 15c4550360c..681d2106d88 100644
--- a/protocol-caps.h
+++ b/protocol-caps.h
@@ -4,5 +4,6 @@
 struct repository;
 struct packet_reader;
 int cap_object_info(struct repository *r, struct packet_reader *request);
+int cap_features(struct repository *r, struct packet_reader *request);
 
 #endif /* PROTOCOL_CAPS_H */
-- 
2.36.0.rc2.902.g60576bbc845