I would like to be able to sync files when the default user of a container has no access to these files

Describe the Feature You Want

In production, the user running code has readonly access on source code. So I would like to ensure that I have the same configuration in development environment.
I my Dockerfile, I have some commands to chmod access to the files sync by Tilt, and to a create and change the default user of the container.
I read in the Tilt documentation that the default user of the container must have access to the files so that Tilt is able to sync files.

Current Behavior

Tilt fails to sync files

Why Do You Want This?

I don't want the user of my container have more rights than in production to ensure that testing done in my development containers have the same behavior that in production.

Additional context
Add any other context or screenshots about the feature request here.

Start with the Dockerfile and the Tilt documentation describing the requirement that the container's default user can access synced files. Reproduce the failure with a container user lacking access, then trace the file-sync entry point. Done means files sync successfully without requiring the container's default user to have broader source-file access.