upload-pack: fix race condition in error messages

Test t5516-fetch-push.sh has a test 'deny fetch unreachable SHA1,
allowtipsha1inwant=true' that checks stderr for a specific error
string from the remote. In some build environments the error sent
over the remote connection gets mingled with the error from the
die() statement. Since both signals are being output to the same
file descriptor (but from parent and child processes), the output
we are matching with grep gets split.

To reduce the risk of this failure, follow this process instead:

1. Write an error message to stderr.
2. Write an error message across the connection.
3. exit(1).

This reorders the events so the error is written entirely before
the client receives a message from the remote, removing the race
condition.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/upload-pack.c b/upload-pack.c
index d3312006a32bebdc67c4395b6468db328b501c86..ece111c629be7156e04c1ee82d1674ef08b4c730 100644 (file)
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -777,11 +777,12 @@ error:
        for (i = 0; i < data->want_obj.nr; i++) {
                struct object *o = data->want_obj.objects[i].item;
                if (!is_our_ref(o, data->allow_uor)) {
+                       error("git upload-pack: not our ref %s",
+                             oid_to_hex(&o->oid));
                        packet_writer_error(&data->writer,
                                            "upload-pack: not our ref %s",
                                            oid_to_hex(&o->oid));
-                       die("git upload-pack: not our ref %s",
-                           oid_to_hex(&o->oid));
+                       exit(1);
                }
        }
 }