Make Action usable inside a Docker container

[akashchi]

Hi,

We are using this action to install Python on ARM machines and the workflow steps are executed inside a container (almost bare ubuntu:20.04).

There is a known problem with github.action_path - it is incorrectly set if the action is executed inside a container: 1, 2. We have encountered it ourselves when trying to use the action. It failed with:

The proposed fix is to check if the install_python script exists under either of the two paths:

• ${{ github.action_path }}/bin/ - for the outside container scenario
• $GITHUB_ACTION_PATH/bin/ - for the inside container scenario

I've added the matrix entry with a Docker image to check if this would work: it works.

[asottile]

this is not intended to be used inside a container -- you're free to maintain your fork which does though!

[ilya-lavrenov]

strange position since using docker images in GHA is quite popular

[asottile]

I'm not going to hack around a bug in github for something I don't intend to support and has a bunch of complexity and problem surface area

[cmarqu]

For anyone doing a web search for the error message, it is
/__w/_temp/97ed7fc6-352d-4a8c-a3a5-50c825ab89c0.sh: line 1: /runner/_work/_actions/deadsnakes/action/v3.1.0/bin/install-python: No such file or directory