pushing to a private registry

[nicks]

If you are not authenticated correctly to a private registry, and you try to build to a remote cluster with Tilt, you will get an a message like this:

Build Failed: pushing image "deadbeef.amazonaws.com/my-image/blahblahblah": no basic auth credentials

A couple notes on auth:

• Tilt will use the registry auth mechanism of your underlying image build tool. So if you use docker_build, Tilt will use the auth credentials of your Docker service. So you don't need to worry about auth when you push the image.

• In local dev environments (Minikube, Docker for Mac, Kind, K3d, Microk8s), Tilt will do as much as it can to deploy your images directly to the cluster (rather than a remote registry). A big reason why we do this is so that you don't have to worry about auth

But users may need help understanding what this message means or how to fix it.

Most AWS users use the ECR credential helper: https://github.com/awslabs/amazon-ecr-credential-helper

GKE users use the gcloud credential helper gcloud auth configure-docker: https://cloud.google.com/sdk/gcloud/reference/auth/configure-docker

Or just docker login

ideally, Tilt might link to a doc of common push issues when you hit this problem

Related issue: #3579