Re: \if, \elseif, \else, \endif (was Re: [HACKERS] PSQL commands:\quit_if, \quit_unless)

> Consolidated Fabien's TAP test additions with v7, in case anyone else wants
> to be reviewing.

Patch applies (with "patch"), make check ok, psql tap test ok.

I did some more tests. I found a subtlety that I missed before: when 
running under ON_ERROR_STOP, messages are not fully consistent:
 sh> cat test.sql \set ON_ERROR_STOP on \if error   \echo NO \endif \echo NO
 sh> ./psql < test.sql SET # ok unrecognized value "error" for "\if <expr>": boolean expected # ok new \if is invalid,
ignoringcommands until next \endif # hmmm... but it does not, it is really stopping immediately... found EOF before
closing\endif(s) # no, it has just stopped before EOF because of the error...
 

Also I'm not quite sure why psql decided that it is in interactive mode 
above, its stdin is a file, but why not.

The issue is made more explicit with -f:
 sh> ./psql -f test.sql SET psql:test.sql:2: unrecognized value "error" for "\if <expr>": boolean expected
psql:test.sql:2:new \if is invalid, ignoring commands until next \endif psql:test.sql:2: found EOF before closing
\endif(s)

It stopped on line 2, which is expected, but it was not on EOF.

I think that the message when stopping should be ", stopping as required 
by ON_ERROR_STOP" or something like that instead of ", ignoring...", and 
the EOF message should not be printed at all in this case.

-- 
Fabien.