Document environment variable precedence

[happz]

Related to #4241

See #4241 for TODO items and tracking.

See https://tmt--4364.org.readthedocs.build/en/4364/environment.html for the preview.

Pull Request Checklist

• implement the feature
• write the documentation
• update the specification
• include a release note

[happz]

Ok, kicking of with a summary and a couple of notes and TODO items while my memory is reasonably fresh.

See https://tmt--4364.org.readthedocs.build/en/4364/environment.html for the preview.

Ignore the location of the document, I just needed to hook it somewhere.

[psss]

Synced priority with the issue and proposed for the next sprint as agreed on the hacking session.

[LecrisUT]

Overall LGTM, only confusion is with the "User"

[LecrisUT]

Is there a different wording we could use here. "User-provided" is a bit loaded and overlaps with the "command line" part. For me the user here is more like the executioner, not the author of the fmf file, so probably that's why it gets more loaded for me.

[happz]

Not having any idea of my own, I'm open to suggestions.

[LecrisUT]

Hmm, some possibilities: "static", "fmf file defined", "author defined" (would need glossary), just "test environment"?

Also for this one in particular it could use a quick note on adjust-test? Or have somewhere to explicitly mention where the fmf file evaluation (and discover) fit in here.

[happz]

I use "user" as a term in contrast to "variables added and owned by tmt", with no distiction between "user who wrote fmf files" and "user who runs tmt run". I believe we don't have dedicated labels for these two roles.