Insert magic tex command for pdf-engine

[jooyoungseo]

When pdf-engine is set to xelatex, for example, it would be even nicer the following magic command can be auto inserted at the top of the tex output:

% !TEX program = xelatex

This is useful when people directly edit and compile the produced tex file in tex editor that can understand these kinds of magic commands.

[jooyoungseo]

Other related tex magic commands: https://www.texdev.net/2011/03/24/texworks-magic-comments/ and http://transit.iut2.upmf-grenoble.fr/doc/texstudio/html/usermanual_en.html

Also, this Stack Exchange discussion might be worth mentioning.

[jgm]

Actually, pandoc does not produce different TeX depending on --pdf-engine; the TeX it produces is all designed to work with all the engines (it uses conditionals).

Nor does --pdf-engine do anything when you're producing tex output -- only pdf.