LaTeX-Box-Team/LaTeX-Box — pull request #19 by jnwhiteh (2012-05-14 14:21:07+00:00)
Title: Add support for specifying the main LaTeX file in a comment

Any line in the first five lines of the file that contains 'root' followed by
any number of spaces, followed by a equals sign, followed by a filename will
work. The typical format is:

%!TEX root = main.tex

To set the main file to main.tex.

This is the same comment used to specify the filename in Texworks.