Capture of stdout / stderr

[arlyon]

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Motivation

It would be nice to be able to capture stdout / stderr on certain commands. My example: I have a workflow which runs a script using cargo make the output of which I'd like to capture and put in a comment on PRs. See here:

https://github.com/arlyon/async-stripe/blob/master/.github/workflows/openapi.yml#L27-L32

The missing part is that outputs.stdout is not actually populated with anything yet.

Workflow example

No proposed changes to the workflow definitions, just populate the stdout / stderr outputs for use in other actions.

Additional context

The run command allows you to do this just fine, but I'd like to use the dedicated action if possible, rather than manually calling cargo make verify.