bug#46351: 28.0.50; Add convenient way to bypass Eshell's own pipelining

[Jim Porter <jporterbugs@gmail.com>]

On 1/24/2022 12:46 PM, Lars Ingebrigtsen wrote:
> Sean Whitton <spwhitton@spwhitton.name> writes:
> 
>> Likewise fixed in the attached.
> 
> Thanks; pushed to Emacs 29.

I just noticed a small bit of breakage with this. It's no longer 
possible to refer to Lisp functions in Eshell like so:

   #'upcase

Eshell explicitly supports this construct (see `eshell-lisp-regexp'), 
though it doesn't appear to be documented in the manual. Currently, this 
syntax is only occasionally useful, but I'm working on a patch series 
where it'll likely become a lot more common. My patches will add support 
for piping to Lisp functions, so that you can do the following, for example:

   $ echo hi | #'upcase
   HI

It looks like the breakage in parsing #'upcase is the result of 
`eshell-parse-external-pipeline' trying to skip over args like '*|' 
(with the quotes). However, it sees the single-quote in #'upcase and 
then calls `eshell-parse-literal-quote', resulting in the error message:

   Expecting completion of delimiter ' ...