transport-helper: check dup() return in get_exporter

get_exporter() duplicates helper->in via dup() and stores the
result in fastexport->out. If dup() fails (fd exhaustion), it
returns -1. The child_process machinery interprets out = -1 as
"create a pipe for stdout", which would silently change the
fast-export process's output wiring: instead of sending data
back through the helper's input fd, it would write to a new pipe
that nobody reads from.

Check the return value and report the error before proceeding.

Pointed out by Coverity.

Assisted-by: Claude Opus 4.6
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions