Design Question: Why not pass parameters as build arguments

[abjrcode]

This is a question regarding the design of both this image and the full build agent docker image.

I am just wondering why not accept the TeamCity URL and other parameters as docker arguments ARG which you supply during building the container and also bake the build agents config file into the contains writable layer?

That way, images provided by JetBrains become always base images used in FROM clauses and the result is a new container image which you can push, say to ECR repository for instance.
It also avoids the need for mount volumes which aren't available in Fargate for instance.

I know I can copy the code and do what I described, I am just wondering why you didn't take that approach from the beginning
Thank you