Re-`use` shell commands?

In several actions, I have the same sequence of run commands that are executed in the shell of the worker node.

Is there a simple way to move those to a dedicated (public) repository and use them?

At first sight, it seems I can only re-use Actions written in JavaScript, those containing a Dockerfile or using Docker containers directly. 

Writing JavaScript to execute a series of shell commands is probably straightforward, but adds unneccessary complexity. A Docker container makes it more complex to mount the necessary volumes and/or is complicated when the Action is to run Docker containers itself.

You can create a shell script file that contains the sequence of commands and call it from the action like run:

No, what I meant is this: