Re: Variable substitution in psql backtick expansion

So I thought we were done bikeshedding the variable names for this
feature, but as I was reviewing the patch with intent to commit,
I noticed you hadn't updated helpVariables() to mention them.
Possibly you missed this because it doesn't mention VERSION either,
but that doesn't seem very defensible.

I inserted text to describe all five variables --- but
"SERVER_VERSION_NAME" is too long to fit in the available column space.
In the attached updated patch, I moved all the descriptive text over one
column, and really should have moved it over two columns; but adding even
one space makes a couple of the lines longer than 80 columns when they
were not before. Since we've blown past 80 columns on some of the other
output, maybe that doesn't matter. Or maybe we should shorten this
variable name so it doesn't force reformatting of all this text.

Possible ideas include "DB_VERSION_NAME", "SERVER_VER_NAME", or
"SERVER_VERSION_STR". (The last saves only one character, whereas
we really need to save two if we're trying not to be wider than any
other documented variable.)

Thoughts?

Attached updated patch changes helpVariables() as we'd need to do if
not renaming, and does some minor doc/comment wordsmithing elsewhere.

regards, tom lane