Replace deprecated GHA ::set-output syntax

[phil9909]

Summary

Fixes #867

Use the new way of producing outputs in a github action as the old way is deprecated and will be removed (31st May 2023).

See https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Use Cases

Pipelines will continue to work after May 31st 2023.

Checklist

• I have viewed, signed, and submitted the Contributor License Agreement.
• I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• I have added an integration test, if necessary.
• I have reviewed the styleguide for guidance on my code quality.
• I'm happy with the commit history on this PR (I have rebased/squashed as needed).

[dmikusa]

This looks good, a few questions/possible adjustments.

In the meantime, I'm going to manually PR this into our test pipeline on paketo-buildpacks/pipeline-builder-canary.

[dmikusa]

Is there a specific reason to not use os.Create(..)? Typically, that is preferred for writing files.

https://pkg.go.dev/os#Create

[phil9909]

os.Create passes the O_TRUNC flag, we pass O_APPEND instead.

Basically the same as >> "$GITHUB_OUTPUT" vs > "$GITHUB_OUTPUT" in bash would be. In their examples GitHub uses append.
I assume, if we truncate the file we would delete outputs that were created elsewhere. This might lead to subtle bugs, as GitHub Actions don't fail on missing values in their interpolation syntax.
So IMHO this is the better option, even if it is less readable.

My suggestions:

• Either I add a comment explaining the difference to os.Open
• or I move the os.OpenFile call to a new helper function called Append, with a doc comment that it works like os.Open, but uses the append instead of the truncate flag.

What would you prefer?

[dmikusa]

Ah ha. Ok. That makes perfect sense, don't want to truncate the file and wipe out previously written output.

To clarify the code I don't have a strong preference, but given a choice, I'd say let's go with the Append method.

[phil9909]

I called the method createOrAppend:

1. I guess it's better private, therefore lowercase
2. append would collide with the built-in array append function.

[dmikusa]

A couple of other things...

1. Please run go generate ./... from the octo/ subdirectory. This will update the statik file, which needs to be updated when the shell scripts are modified.
2. Please bump mheap/github-action-required-labels@v2 to mheap/github-action-required-labels@v3. That should update that action to a newer version which doesn't use ::set-output.

Thanks

[phil9909]

1. Please run go generate ./... from the octo/ subdirectory. This will update the statik file, which needs to be updated when the shell scripts are modified.
2. Please bump mheap/github-action-required-labels@v2 to mheap/github-action-required-labels@v3. That should update that action to a newer version which doesn't use ::set-output.

Done