[Orgmode] Using HTML export variables in subtrees

[Jeff Horn]

Is there a way to turn off the automatic post-amble for HTML export
without adding a publishing project? I am making extensive use of
subtree exporting, and I'd like to turn off the automatic postamble
for some some of these subtrees.

Adding a file local variable didn't work (I suspect) because the
variables are used by publishing functions and those functions are
looking somewhere else. In any case, `org-export-html-auto-postamble`
doesn't seem exposed to user customization.

-- 
Jeffrey Horn
http://www.failuretorefrain.com/jeff/