Re: pgsql: Add basic TAP tests for psql's tab-completion logic.

Re: Robert Haas 2020-01-09 <CA+TgmoZC_6z3d5+6n1GVfy898uoBHMPPJU4-nAQLG5ZkaEyqdQ@mail.gmail.com>
> > So that raises the question: why does xenial's version of libedit
> > not match either its documentation or the distributed source code?
> > Because it doesn't.
> 
> The level of effort you've put into this is extremely impressive, but
> I can't shake the feeling that you're going to keep finding issues in
> the test setup, the operating system, or the upstream libraries,
> rather than bugs in PostgreSQL. Maybe this is all just one-time
> stabilization effort, but...

Fwiw if libedit in xenial is Just Broken and fixing the tests would
just codify the brokenness without adding any value, I'll just disable
that test in that particular build. It looks like setting
with_readline=no on the make command line should work.

Christoph