upload-pack spawns two processes, rev-list and pack-objects, and carefully
monitors their status so that it can report failure to the remote end.
This change removes the complicated procedures on the grounds of the
following observations:
- If everything is OK, rev-list closes its output pipe end, upon which
pack-objects (which reads from the pipe) sees EOF and terminates itself,
closing its output (and error) pipes. upload-pack reads from both until
it sees EOF in both. It collects the exit codes of the child processes
(which indicate success) and terminates successfully.
- If rev-list sees an error, it closes its output and terminates with
failure. pack-objects sees EOF in its input and terminates successfully.
Again upload-pack reads its inputs until EOF. When it now collects
the exit codes of its child processes, it notices the failure of rev-list
and signals failure to the remote end.
- If pack-objects sees an error, it terminates with failure. Since this
breaks the pipe to rev-list, rev-list is killed with SIGPIPE.
upload-pack reads its input until EOF, then collects the exit codes of
the child processes, notices their failures, and signals failure to the
remote end.
- If upload-pack itself dies unexpectedly, pack-objects is killed with
SIGPIPE, and subsequently also rev-list.
The upshot of this is that precise monitoring of child processes is not
required because both terminate if either one of them dies unexpectedly.
This allows us to use finish_command() and finish_async() instead of
an explicit waitpid(2) call.
The change is smaller than it looks because most of it only reduces the
indentation of a large part of the inner loop.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
