command: Add redirect support to 0.13upgrade

[alisdair]

If a provider changes namespace in the registry, we can detect this when running the 0.13upgrade command. As long as there is a version matching the user's constraints, we now use the provider's new source address. Otherwise, warn the user that the provider has moved and a version upgrade is necessary to move to it.

Screenshots

Successful provider redirect, due to version constraint being met by the redirect target:

Cannot follow the redirect, as the version constraint cannot be met:

[codecov]

Codecov Report

Merging #26061 into master will decrease coverage by 0.01%.
The diff coverage is 48.54%.

Impacted Files	Coverage Δ
command/013_config_upgrade.go	71.45% <41.93%> (-4.56%)	⬇️
internal/getproviders/registry_client.go	65.91% <45.00%> (-0.43%)	⬇️
internal/getproviders/registry_source.go	68.96% <50.00%> (ø)
command/init.go	66.66% <60.00%> (-0.17%)	⬇️
internal/getproviders/legacy_lookup.go	51.28% <78.57%> (+8.85%)	⬆️
dag/marshal.go	54.44% <0.00%> (+1.11%)	⬆️

[mildwonkey]

This could be unclear to users - do you mean upgrade terraform, or upgrade the pinned provider version? It's also not quite clear that this is optional. This is my awkward take at the message, it's not necessarily better, just want to see what you think:

"Provider %q has moved to %q. No action is required to continue using %q (provider) version %q (their constraint), but if you want to upgrade beyond version %s (last version available at the old location) you must also update the source:

[pkolyvas]

I think this is a great suggestion!

[alisdair]

Great idea, thanks! Here's the warning I ended up with:

[mildwonkey]

This is a great update, thank you!

I left some nitpicky thoughts about the warning when the provider has moved but the config is pinned to the older (pre-move) version of the provider, but they are not meant to block merging - you can modify the message on your own, or not, and I still approve ✅

[justincampbell]

This looks great to me from the Registry point of view. Thanks!

[ghost]

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