RFE: Run all environments by default

[hroncok]

Currently, the actions runs tox with -e${{ inputs.tox_env }}. The value is required and the default is py38.

As a consequence, I need to have the environments listed in 2 places, which I don't particularly like. The default should IMHO be the run all of them. Or at least, this should be an option.

[encukou]

I like to have individual environments show up as separate tests on GitHub, and I haven't found a way to do this while taking the list of all environments from Tox.

[hroncok]

I see (and I have kinda figured that out in the meantime). Let's document this?

[encukou]

Apparently this can be done now: https://github.com/tox-dev/gh-action-tox/blob/experiments/composite-action/.github/workflows/call-tox.yml

[medmunds]

I just released a tox plugin to try to address this: https://pypi.org/project/tox-gh-matrix/. It generates a JSON version of the tox envlist, which can be used to create a GH workflow build matrix with fromJSON().

(I had the same need for a project I maintain, and stumbled across this issue while looking to see if anyone else had solved the problem.)