Add --help=<topic> for the commandline, and \? <topic> as a backslash
command, to show more help than the invocations without parameters
do. "commands", "variables" and "options" currently exist as help
topics describing, respectively, backslash commands, psql variables,
and commandline switches. Without parameters the help commands show
their previous topic.
Some further wordsmithing or extending of the added help content might
be needed; but there seems little benefit delaying the overall feature
further.
Author: Pavel Stehule, editorialized by many
Reviewed-By: Andres Freund, Petr Jelinek, Fujii Masao, MauMau, Abhijit
Menon-Sen and Erik Rijkers.
Discussion: CAFj8pRDVGuC-nXBfe2CK8vpyzd2Dsr9GVpbrATAnZO=2YQ0s2Q@mail.gmail.com,
CAFj8pRA54AbTv2RXDTRxiAd8hy8wxmoVLqhJDRCwEnhdd7OUkw@mail.gmail.com
07c8651dd9