Re: authentication/t/001_password.pl trashes ~/.psql_history

I wrote:
> I happened to notice this stuff getting added to my .psql_history:
> \echo background_psql: ready
> SET password_encryption='scram-sha-256';
> ;
> \echo background_psql: QUERY_SEPARATOR
> SET scram_iterations=42;
> ;
> \echo background_psql: QUERY_SEPARATOR
> \password scram_role_iter
> \q

> After grepping for these strings, this is evidently the fault of
> src/test/authentication/t/001_password.pl by way of BackgroundPsql.pm,
> which fires up an interactive psql run that is not given the -n switch.

> Currently the only other user of interactive_psql() seems to be
> psql/t/010_tab_completion.pl, which avoids this problem by
> explicitly redirecting the history file. We could have 001_password.pl
> do likewise, or we could have it pass the -n switch, but I think we're
> going to have this problem resurface repeatedly if we leave it to the
> outer test script to remember to do it.

After studying this some more, my conclusion is that BackgroundPsql.pm
failed to borrow as much as it should have from 010_tab_completion.pl.
Specifically, we want all the environment-variable changes that that
script performed to be applied in any test using an interactive psql.
Maybe ~/.inputrc and so forth would never affect any other test scripts,
but that doesn't seem like a great bet.

So that leads me to the attached proposed patch.

regards, tom lane