Custom Javascript code upload automation

Does anyone know if it’s possible and how to upload my Javascript code file to the URL as specified in this page?
Knack: What’s New?

I’m referring to those two URLs:<your_application_id>/custom/main.js

My code uses three separate files:

  1. a bootloader
  2. my app-specific code
  3. the Knack Toolkit Library (KTL)

Every time I want to make a release, I need to assemble them into a merged file (using a simple NodeJS script), open that file, select all code, copy/paste it in the Builder’s Javascript pane and save.

I would like to automate all this process in a single click. The only show stopper is how to upload my file to the CDN. Is there some kind of SFTP trick? A hidden API call?