Merge branch 'af/clone-revision-v0-segfault-fix'

A segfault when 'git clone --revision' talks to a server that does not
support protocol v2 (falling back to protocol v0) has been corrected.

* af/clone-revision-v0-segfault-fix:
  builtin/clone: fix segfault when using --revision with protocol v0

Author: gitster

builtin/clone.c

@@ -557,7 +557,7 @@ static void update_remote_refs(const struct ref *refs,
 			write_followtags(refs, msg);
 	}
 
-	if (remote_head_points_at && !option_bare) {
+	if (remote_head_points_at && remote_head_points_at->peer_ref && !option_bare) {
 		struct strbuf head_ref = STRBUF_INIT;
 		strbuf_addstr(&head_ref, branch_top);
 		strbuf_addstr(&head_ref, "HEAD");

t/t5621-clone-revision.sh

@@ -90,6 +90,14 @@ test_expect_success 'clone with --revision and --bare' '
 	test_must_fail git -C dst config remote.origin.fetch
 '
 
+test_expect_success 'clone with --revision and protocol v0' '
+	test_when_finished "rm -rf dst" &&
+	git -c protocol.version=0 clone --no-local --revision=refs/heads/main . dst &&
+	git rev-parse refs/heads/main >expect &&
+	git -C dst rev-parse HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'clone with --revision being a short raw commit hash' '
 	test_when_finished "rm -rf dst" &&
 	oid=$(git rev-parse --short refs/heads/feature) &&