First, I'll post an example how I "think" it may be defined in a Brunch configuration file:
So if you have this folder structure, you would get the following output:
brunch_project/ app_300x250/ other.js app.js index.html app_728x90/ other.js app.js index.html public/ app_300x250.js app_300x250.html app_728x90.js app_728x90.html vendor.js
True, I didn't show in the configuration how the HTML would get renamed/merged the same as the JS files, but that's how I'd like it to work ideally. Bonus high-fives for anyone who shows me how it's done!
If you have only two variants, i'd suggest to just add files like
assets/ directories. Then, create subfolders with resolutions inside
app/. And use it in regexps.
joinTo clause like that: