TLDR; Check it our yourself:
Who is it for?
It's a helper tool for all fortrabbit clients running Craft 3 in a "sophisticated way": Having a local development environment setup, deploying the code base with Git, syncing assets with rsync, authenticating with an SSH key, being familiar with the command line.
What does it do?
It's basically a wrapper for
rsync (both are required locally) — also including some magic. It connects your fortrabbit App with your local development environment. Deploying with Git is convenient at fortrabbit, but it's only part of the deployment. This tool helps with all the other parts:
It will check if your setup is complete or if certain parts are missing.
Craft Copy helps you keeping the databases in sync. You can easily sync the database up (from your local dev env to production at fortrabbit) and down (from production at fortrabbit to your local dev env).
And you can sync the assets — think uploads — with rsync up and down.
Only for fortrabbit?
Yep, sorry. Currently only fortrabbit is supported, as this is a standardized environment. Craft Copy is also still in BETA. Please contribute, it's open source!