fetch: generate ref-prefixes when using a configured refspec

Teach fetch to generate ref-prefixes, to be used for server-side
filtering of the ref-advertisement, based on the configured fetch
refspec ('remote.<name>.fetch') when no user provided refspec exists.

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

builtin/fetch.c

@@ -351,7 +351,15 @@ static struct ref *get_ref_map(struct transport *transport,
 
 	const struct ref *remote_refs;
 
-	refspec_ref_prefixes(rs, &ref_prefixes);
+	if (rs->nr)
+		refspec_ref_prefixes(rs, &ref_prefixes);
+	else if (transport->remote && transport->remote->fetch.nr)
+		refspec_ref_prefixes(&transport->remote->fetch, &ref_prefixes);
+
+	if (ref_prefixes.argc &&
+	    (tags == TAGS_SET || (tags == TAGS_DEFAULT && !rs->nr))) {
+		argv_array_push(&ref_prefixes, "refs/tags/");
+	}
 
 	remote_refs = transport_get_remote_refs(transport, &ref_prefixes);
 

t/t5702-protocol-v2.sh

@@ -201,6 +201,20 @@ test_expect_success 'ref advertisment is filtered during fetch using protocol v2
 	! grep "refs/tags/three" log
 '
 
+test_expect_success 'default refspec is used to filter ref when fetchcing' '
+	test_when_finished "rm -f log" &&
+
+	GIT_TRACE_PACKET="$(pwd)/log" git -C file_child -c protocol.version=2 \
+		fetch origin &&
+
+	git -C file_child log -1 --format=%s three >actual &&
+	git -C file_parent log -1 --format=%s three >expect &&
+	test_cmp expect actual &&
+
+	grep "ref-prefix refs/heads/" log &&
+	grep "ref-prefix refs/tags/" log
+'
+
 # Test protocol v2 with 'http://' transport
 #
 . "$TEST_DIRECTORY"/lib-httpd.sh