Switch Logstash repo from master to main for doc builds

[karenzone]

Sets up the docs build to pull from the "main" branch of the Logstash repo instead of the "master" branch.

Related: elastic/logstash#12052

[gtback]

Looks good to me!

We could temporarily create a main branch that's equivalent to master in order to test this (then remove it before doing the actual rename to keep the redirects GitHub will set up).

I'm assuming both logstash and logstash-docs will get renamed at the same time?

---

The VPR shouldn't be affected since it doesn't use the main or master branches. But I'm suprised how this ever worked without a map_branches since there's no versioned_plugin_docs branch in the docs repo:

          - title:      Logstash Versioned Plugin Reference
            prefix:     en/logstash-versioned-plugins
            current:    versioned_plugin_docs
            branches:   [ versioned_plugin_docs ]
            index:      docs/versioned-plugins/index.asciidoc
...
            sources:
              -
                repo:   logstash-docs
                path:   docs/versioned-plugins
              -
                repo:   docs
                path:   shared/attributes.asciidoc

[karenzone]

I'm assuming both logstash and logstash-docs will get renamed at the same time?

Yes, that is the plan.

The VPR shouldn't be affected...

That's the logic I'm going on. The VPR lives on its own branch that's not named either master or main, so it should not be affected. But as we all know, the VPR is a sneaky little devil. :-D

Thanks for the reviews/comments/approvals, @lcawl and @gtback ❤️

[jsvd]

@gtback @lcawl hi friend, I've just updated the elastic/logstash and elastic/logstash-docs master branch to main, can this be merged now?

[jsvd]

@elasticmachine run elasticsearch-ci/docs

[gtback]

Thanks for merging this, @jsvd !