Option for latest released version of Emacs?

[countvajhula]

Hi, thanks for making this recipe!

In some of my test scripts (in particular, for running coverage) I'd like to install a reasonably safe version of Emacs and it doesn't matter what that version is. The only considerations are that it shouldn't be too old/irrelevant and that it shouldn't be too new/unstable. I wouldn't want to use snapshot here since that may be unstable, and using 27.1 or some specific version also doesn't seem ideal since over time this might become increasingly stale and might warrant some maintenance to periodically update this to a more recent stable version (esp. if the package eventually drops support for this version).

Instead, it'd be nice to have a release or latest option to use here, which always points to the latest released version of Emacs.

[purcell]

I was thinking about doing this recently. Generally it's kinda better if the builds are completely reproducible over time for any given config, but snapshot already breaks that assumption. I have a feeling there was some potential issue with the plan — I'll have a think and see if I can remember, otherwise I'll go ahead with this.

[countvajhula]

That makes sense, too, though you're right snapshot is an exception to that already.

I guess one possible way to resolve both could be to accept a timestamp as a parameter in some way, so that if we say something like:

steps:
    - name: Get current date
      id: date
      run: echo "::set-output name=date::$(date +'%Y-%m-%d')"
    - name: Install Emacs
      uses: purcell/setup-emacs@master
      with:
        date: ${{ steps.date.outputs.date }}
        version: ${{ matrix.emacs_version }}

... then it would pull the release or snapshot version in relation to the provided date.

The date recipe is from https://stackoverflow.com/questions/60942067/get-current-date-and-time-in-github-workflows