Yes! flyctl auth docker does the Docker login for our registry, so if you have a build process somewhere that pushes to GCR, you could add a push to Fly step. You’d basically:
flyctl auth dockerdocker tag <image-ref> registry.fly.io/<fly-app-name>:latestdocker push registry.fly.io/<fly-app-name>:latest
I think that’s the right tag command. I never can remember.
Then: flyctl deploy -i registry.fly.io/<fly-app-name>:latest