Can I git pull from a fly.io remote?

It looks like I’m still missing some files.

$ fly deploy -a APPNAME
Update available 0.0.390 -> v0.0.391.
Run "fly version update" to upgrade.
==> Verifying app config
--> Verified app config
==> Building image
Error failed to fetch an image or build from source: app does not have a Dockerfile or buildpacks configured. See https://fly.io/docs/reference/configuration/#the-build-section

The error message points to the build section which talks about the build, buildpacks, or a docker image. The fly.toml file that I copied via fly config save -a APPNAME doesn’t have any of those sections. I’m not sure why it wouldn’t be accurate since I just copied it down. Do you know how I can copy a dockerfile? Based on what this person says, I’m thinking I need one. Strangely, the docs for building a new rails app don’t mention needing a dockerfile or buildpacks.