Clarify nature of GITHUB_ENV/GITHUB_PATH variables

[davidjb]

Why:

When reading the existing documentation at https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#setting-an-environment-variable, I was under the impression that $GITHUB_ENV and $GITHUB_PATH would both be applied in the same way, both being available as environment variables within a given shell (the run command) in subsequent steps. However, the former requires explicit referencing in expression syntax (or use of the $GITHUB_ENV file directly) whereas the latter is introduced in the shell environment's $PATH automatically. The docs don't currently state this; they allude to it in various other pages but not specifically spell this out.

Closes #9235

What's being changed:

This adds a note and clarification around the explicit nature of using $GITHUB_ENV but the implicit, automatic application of $GITHUB_PATH.

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[ramyaparimi]

@davidjb Thanks so much for opening a PR! I'll get this triaged for review ⚡

[L2021]

Its interesting

[L2021]

Keep it up friend

[skedwards88]

🎉 Thanks for making this addition! I'll get this merged down for you.

[ramyaparimi]

@davidjb It looks like I don't have permission to resolve the merge conflict. I think if you enable the checkbox to allow maintainer edits, then I will be able to resolve this. (https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests/allowing-changes-to-a-pull-request-branch-created-from-a-fork ) Alternatively, could you resolve the merge conflict?

[davidjb]

@ramyaparimi the checkbox was already enabled so hopefully that’s good to go. Otherwise, I can take a look tomorrow and rebase the changes.

[ramyaparimi]

Approving again after resolving conflicts!

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