bug#29157: 25.3; Eshell parsing fails sometimes, e.g. "date" and "sed"

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@users.sourceforge.net>
> Cc: 29157@debbugs.gnu.org,  ambrevar@gmail.com
> Date: Sat, 25 Nov 2017 15:06:01 -0500
> 
> >   ~ $ date 42 "EDT-5"
> >   Thu Jan  1 05:00:42 1970
> >   ~ $ date (list 23065 51329 644000 0)
> >   Sat Nov 25 21:46:09 2017
> 
> Ugh, stop taking me so literally, and just read my mind! ;P
> 
> How about checking for a set of arguments that is compatible with what
> current-time-string accepts.

Is it really possible to do that reliably?

Or maybe you meant to catch errors signaled by current-time-string,
and invoke the external command then.  If so, I'd agree.  But we
should then allow customization of the external command's name,
because on Windows it will be something like 'gdate', to avoid calling
the incompatible Windows shell's built-in (which also prompts
interactively for input).