[PATCH 20/25] serve: understand but do not advertise 'features' capability

From: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: gitster@pobox.com, me@ttaylorr.com, aevar@gmail.com,
	newren@gmail.com, Derrick Stolee <derrickstolee@github.com>,
	Derrick Stolee <derrickstolee@github.com>
Subject: [PATCH 20/25] serve: understand but do not advertise 'features' capability
Date: Wed, 23 Feb 2022 18:30:58 +0000	[thread overview]
Message-ID: <5b983cc3c104fe6ed64608320387bf82fefcdbb4.1645641063.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1160.git.1645641063.gitgitgadget@gmail.com>

From: Derrick Stolee <derrickstolee@github.com>

The previous change implemented cap_features() to return a set of
'key=value' pairs when this capability is run. Add the capability to our
list of understood capabilities.

This change does not advertise the capability. When deploying a new
capability to a distributed fleet of Git servers, it is important to
delay advertising the capability until all nodes understand it. A later
change will advertise it when appropriate, but as a separate change to
simplify this transition.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
---
 serve.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/serve.c b/serve.c
index b3fe9b5126a..a1c853dda1f 100644
--- a/serve.c
+++ b/serve.c
@@ -18,6 +18,12 @@ static int always_advertise(struct repository *r,
 	return 1;
 }
 
+static int never_advertise(struct repository *r,
+			   struct strbuf *value)
+{
+	return 0;
+}
+
 static int agent_advertise(struct repository *r,
 			   struct strbuf *value)
 {
@@ -136,6 +142,11 @@ static struct protocol_capability capabilities[] = {
 		.advertise = always_advertise,
 		.command = cap_object_info,
 	},
+	{
+		.name = "features",
+		.advertise = never_advertise,
+		.command = cap_features,
+	},
 };
 
 void protocol_v2_advertise_capabilities(void)
-- 
gitgitgadget

