bundle-uri client: add boolean transfer.bundleURI setting

The yet-to-be introduced client support for bundle-uri will always
fall back on a full clone, but we'd still like to be able to ignore a
server's bundle-uri advertisement entirely.

The new transfer.bundleURI config option defaults to 'false', but a user
can set it to 'true' to enable checking for bundle URIs from the origin
Git server using protocol v2.

Co-authored-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/transfer.txt

@@ -115,3 +115,9 @@ transfer.unpackLimit::
 transfer.advertiseSID::
 	Boolean. When true, client and server processes will advertise their
 	unique session IDs to their remote counterpart. Defaults to false.
+
+transfer.bundleURI::
+	When `true`, local `git clone` commands will request bundle
+	information from the remote server (if advertised) and download
+	bundles before continuing the clone through the Git protocol.
+	Defaults to `false`.

t/lib-bundle-uri-protocol.sh

@@ -85,10 +85,11 @@ test_expect_success "connect with $BUNDLE_URI_PROTOCOL:// using protocol v2: hav
 '
 
 test_expect_success "clone with $BUNDLE_URI_PROTOCOL:// using protocol v2: request bundle-uris" '
-	test_when_finished "rm -rf log cloned" &&
+	test_when_finished "rm -rf log cloned cloned2" &&
 
 	GIT_TRACE_PACKET="$PWD/log" \
 	git \
+		-c transfer.bundleURI=false \
 		-c protocol.version=2 \
 		clone "$BUNDLE_URI_REPO_URI" cloned \
 		>actual 2>err &&
@@ -99,6 +100,22 @@ test_expect_success "clone with $BUNDLE_URI_PROTOCOL:// using protocol v2: reque
 	# Server advertised bundle-uri capability
 	grep "< bundle-uri" log &&
 
+	# Client did not issue bundle-uri command
+	! grep "> command=bundle-uri" log &&
+
+	GIT_TRACE_PACKET="$PWD/log" \
+	git \
+		-c transfer.bundleURI=true \
+		-c protocol.version=2 \
+		clone "$BUNDLE_URI_REPO_URI" cloned2 \
+		>actual 2>err &&
+
+	# Server responded using protocol v2
+	grep "< version 2" log &&
+
+	# Server advertised bundle-uri capability
+	grep "< bundle-uri" log &&
+
 	# Client issued bundle-uri command
 	grep "> command=bundle-uri" log
 '

transport.c

@@ -1516,6 +1516,7 @@ int transport_fetch_refs(struct transport *transport, struct ref *refs)
 
 int transport_get_remote_bundle_uri(struct transport *transport)
 {
+	int value = 0;
 	const struct transport_vtable *vtable = transport->vtable;
 
 	/* Check config only once. */
@@ -1523,6 +1524,13 @@ int transport_get_remote_bundle_uri(struct transport *transport)
 		return 0;
 	transport->got_remote_bundle_uri = 1;
 
+	/*
+	 * Don't request bundle-uri from the server unless configured to
+	 * do so by the transfer.bundleURI=true config option.
+	 */
+	if (git_config_get_bool("transfer.bundleuri", &value) || !value)
+		return 0;
+
 	if (!vtable->get_bundle_uri)
 		return error(_("bundle-uri operation not supported by protocol"));