How do I add this to my ./site/composer.json file?

[s3w47m88]

Forgive my ignorance, but Composer is abstract to me and I'm relatively new to it.

How do I add this to my ./site/composer.json file?

[jasperf]

At https://packagist.org/packages/trellis-sync/trellis-sync is the composer package for this repository. It has actually just been added as you asked about it. It has not been tested, but should work running composer require trellis-sync/trellis-sync . Let me know how that goes.
NB Do backup all first!

[s3w47m88]

Great. Thank you for clarifying!