pg_hba_file_settings view patch

Hi All,

While working on pg_hba_lookup function that can be used to lookup for an client
authentication that can be matched for given input parameters, Tom raised some
concrete use case issues in the following mail [1]. In this same
thread, he raised
some advantages of having a view similar like pg_file_settings view
for pg_hba.conf
also.

Here I attached a patch that implements the pg_hba_file_settings view
that displays
all the rows in pg_hba.conf. In case if any error exists in the
authentication rule, the
corresponding error is displayed similar like pg_file_settings.

This view can be used to verify whether there exists any problems or
not in the pg_hba.conf
before it reloads into the system. This view cannot be used to check
similar like
pg_hba_lookup function to find out which rule maps to the
corresponding input connection.

comments?

[1] - https://www.postgresql.org/message-id/28434.1468246200%40sss.pgh.pa.us

Regards,
Hari Babu
Fujitsu Australia