website: keep previous patch release versions' URLs intact

[srenatus]

Currently, whenever there's a patch release, like 0.36.1, that becomes the only displayed docs version in the version picker:

That's fine. However, we also stop generating website content for the previous versions, so 0.36.0 disappears: https://www.openpolicyagent.org/docs/v0.36.0/ is a 404 now.

It would be preferable if those URLs stayed intact.

This could be achieved by some clever redirect logic, or by checking out all the releases in load-docs.sh, and only adding the latest ones of each minor series to the releases.yaml file.

💭 I think the redirect approach would be preferable, since there's less static content to process. But I also don't know off-hand how to get that done.

[srenatus]

It looks like we could achieve the redirect using a hugo feature: Aliases:

For every file docs/website/generated/docs/v*/*.md that load-docs.sh creates, say, docs/website/generated/docs/v0.x.y/envoy-primer.md,

• extract the semver v0.x.y from the path,
• for every v0.x.a with a < y, (e.g. v0.36.0, v0.36.1, v0.36.2 if x is 36 and y is 3)
• add a modified path, /docs/v0.x.a/something/ to the original something.md's frontmatter yaml.

In that example, we'd add

aliases: [/docs/v0.36.0/envoy-primer/, /docs/v0.36.1/envoy-primer/, /docs/v0.36.2/envoy-primer/]

to docs/website/generated/docs/v0.36.3/envoy-primer.md.

Generating the HTML via hugo, it would create stubs for every alias directory, as described here.

[stale]

This issue has been automatically marked as inactive because it has not had any activity in the last 30 days.

[srenatus]

I think I've found a simpler way: #4598 has the wip.