pipe_command(): handle ENOSPC when writing to a pipe

When write() to a non-blocking pipe fails because the buffer is full,
POSIX says we should see EAGAIN. But our mingw_write() compat layer on
Windows actually returns ENOSPC for this case. This is probably
something we want to correct, but given that we don't plan to use
non-blocking descriptors in a lot of places, we can work around it by
just catching ENOSPC alongside EAGAIN. If we ever do fix mingw_write(),
then this patch can be reverted.

We don't actually use a non-blocking pipe yet, so this is still just
preparation.

Helped-by: René Scharfe <[email protected]>
Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

run-command.c

@@ -1377,7 +1377,8 @@ static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 				    io->u.out.len <= MAX_IO_SIZE ?
 				    io->u.out.len : MAX_IO_SIZE);
 			if (len < 0) {
-				if (errno != EINTR && errno != EAGAIN) {
+				if (errno != EINTR && errno != EAGAIN &&
+				    errno != ENOSPC) {
 					io->error = errno;
 					close(io->fd);
 					io->fd = -1;