bug#56025: 29.0.50; em-extpipe-test-2 times out on EMBA and Cygwin

[Sean Whitton <spwhitton@email.arizona.edu>]

Hello,

On Fri 24 Jun 2022 at 04:03pm -07, Jim Porter wrote:

>    When [EOF is] received, all the bytes waiting to be read are
>    immediately passed to the process without waiting for a <newline>, and
>    the EOF is discarded. Thus, if there are no bytes waiting (that is,
>    the EOF occurred at the beginning of a line), a byte count of zero
>    shall be returned from the read(), representing an end-of-file
>    indication.
>
> I interpret that to mean that the preferred way to indicate end-of-file
> to `rev' in this case is to send it "hi [NL] [EOF]". The second EOF that
> Eshell sends when closing the stderr output handle is superfluous, but
> it works fine as far as I can tell.
>
> [1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap11.html

The text states unconditionally that when an EOF is received it is
discarded by the OS.  So we can infer that it's fine to send three,
according to the standard -- it's not just that it happens to work.

Thanks again for working on this.

-- 
Sean Whitton