Re: doc: Document how to run regression tests with custom server settings

Hi

I was doing regression testing according to the PG-doc at [1].
The modification at 854434c5 seems not correct, could you please take a check at it?

>make check PGOPTIONS="-c log_checkpoints=on -c work_mem=50MB"

The above command reported an error like this:
failed: FATAL:  parameter "log_checkpoints" cannot be changed now

IMHO, as a sighup GUC, log_checkpoints can't be set in PGOPTIONS, is that correct?

>make check EXTRA_REGRESS_OPTS="--temp-config=test_postgresql.conf"

pg_regress: could not open "test_postgresql.conf" to read extra config: No such file or directory

I fixed above problem using command like this:
make check EXTRA_REGRESS_OPTS="--temp-config=$(pwd)/test_postgresql.conf"

Maybe we can change doc description to tell user he/she should specify the location of " test_postgresql.conf", thoughts?

[1] https://www.postgresql.org/docs/devel/regress-run.html