[PATCH] print help from psql when user tries to run pg_restore, pg_dump etc

New users frequently attempt to run PostgreSQL's command line utilities
from the psql prompt.

They tend to be confused when this appears to do absolutely nothing:

psql=> pg_restore
psql->

since they're generally not going to semicolon-terminate the command either.

The attached patch detects common command names when they appear first on a
new input line prints a help message. If the buffer is empty a more
detailed message is printed and the input is swallowed. Otherwise, much
like how we handle "help" etc,
a short message is printed and the input is still added to the buffer.

psql=> pg_restore
"pg_restore" is a command line utility program.
Use it from the system terminal or command prompt not from psql.
psql=>
psql=> select 1
psql-> pg_restore
"pg_restore" is a command-line utility program not a psql command. See
"help".
psql->

Wording advice would be welcome.

I'd be tempted to backpatch this, since it's one of the things I see users
confused by most often now - right up there with pg_hba.conf issues,
forgetting a semicolon in psql, etc.

--
Craig Ringer http://www.2ndQuadrant.com/
2ndQuadrant - PostgreSQL Solutions for the Enterprise