How to grant npm and git credentials so that `yarn` can install private npm packages and from git

[cspotcode]

I need to grant our SourceGraph instance access to private npm packages and to install git dependencies straight from git. I can docker exec into the language server's container and configure them manually, and it would be easy for me to write a shell script to do this automatically. I could also create my own docker image based on your language server image. But I'm not sure how to hook this into the sourcegraph server.

Is there a way to specify that the SourceGraph server should launch my custom image? Or, alternatively, is there a way to configure a shell script to run every time the language server's container is updated or rebooted?

Failing that, I'll write a cron job that runs every few minutes, checks if the container has restarted, and if not, runs my script. But I feel like this is a common issue and there's probably a config flag I'm missing. Thanks!