format pdflatex --sections_up to prompt sections to chapters

[schuang]

When I use 7 = for section titles in .do.txt source and run doconce format pdflatex --sections_up, \section{} in the .tex file is promoted to \chapter{} as expected, but \documentclass still uses article (not book), causing pdflatex command to fail (e.g. article does not support \chapter)

I could get around this problem by some preprocessing, but it would be great if article can also be promoted to book when 7 = is prompted to 9 by --sections_up, to avoid pdflatex errors.

Test:

$ cat intro.do.txt 
======= Introduction =======

This is the intro.

$ doconce format pdflatex intro --sections_up
translating doconce text in intro.do.txt to pdflatex
transforming sections: section to chapter...
transforming sections: subsection to section...
transforming sections: subsubsection to subsection...
output in intro.p.tex
$ doconce ptex2tex intro
output in intro.tex
$ cat intro.tex
...<snipped>
\documentclass[%
twoside,                 % oneside: electronic viewing, twoside: printing
final,                   % or draft (marks overfull hboxes, figures with paths)
10pt]{article}
...<snipped>
\chapter{Introduction}

[hplgit]

Fixed!