Add a tool-versions-folder param to specify non-standard .tool-versions locations

[rtyley]

guardian/setup-scala has assumed that the .tool-versions file will always be in the current working directory, but that's not always the case - eg: https://github.com/guardian/janus/pull/4527

One option to get around that, I think, would be to set working-directory: when invoking guardian/setup-scala:

    - name: Install Scala
      uses: guardian/setup-scala@v1
      working-directory: janus

...but maybe allowing specific-configuration of where this specific file is located is more expressive or future-proof?

    - name: Install Scala
      uses: guardian/setup-scala@v1
      tool-versions-folder: janus

[davidfurey]

Looks reasonable to me as long as Adam still thinks this is useful

[JamieB-gu]

Given that you ultimately need the path to the file rather than the folder, would it make sense to ask for that to be specified directly instead? It looks like this is a pattern common to some of the GH actions?

• https://github.com/actions/setup-node/blob/main/docs/advanced-usage.md#node-version-file
• https://github.com/actions/setup-java/blob/main/docs/advanced-usage.md#Java-version-file

[adamnfish]

Really interesting, thanks! The reason I closed the Janus PR and didn't press here for a change is that I'm not certain this action needs to do loads of work to accomodate weird edge cases like that build. I would have waitied to see if it comes up more regularly!

I actually don't hate the idea of using the working directory approach, that hadn't occurred to me! I think that makes this "regular" in a way that specifying this as bespoke configuration does not.

It looks like either approach will work with the underlying actions/setup-java (e.g. the sbt cache), so maybe we start with the no-code version for now and I try the working directory?

[rtyley]

It looks like either approach will work with the underlying actions/setup-java (e.g. the sbt cache), so maybe we start with the no-code version for now and I try the working directory?

Sure, I'll close this PR for now!