protocol-caps.c: fix memory leak in send_info()

Fix a memory leak in a2ba162 (object-info: support for retrieving
object info, 2021-04-20) which appears to have been based on a
misunderstanding of how the pkt-line.c API works. There is no need to
strdup() input to packet_writer_write(), it's just a printf()-like
format function.

This fixes a potentially large memory leak, since the number of OID
lines the "object-info" call can be arbitrarily large (or a small one
if the request is small).

This makes t5701-git-serve.sh pass again under SANITIZE=leak, as it
did before a2ba162.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Acked-by: Bruno Albuquerque <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

protocol-caps.c

@@ -69,9 +69,10 @@ static void send_info(struct repository *r, struct packet_writer *writer,
 			}
 		}
 
-		packet_writer_write(writer, "%s",
-				    strbuf_detach(&send_buffer, NULL));
+		packet_writer_write(writer, "%s", send_buffer.buf);
+		strbuf_reset(&send_buffer);
 	}
+	strbuf_release(&send_buffer);
 }
 
 int cap_object_info(struct repository *r, struct strvec *keys,