ReadTheDocs has no 'stable' version

[david-cortes]

Previously, the readthedocs page had a 'stable' version which pointed to the last stable release.

But there's no such tag anymore, so links like this throw 404:
https://xgboost.readthedocs.io/en/stable/index.html

[trivialfis]

It was replaced by the release_3.0.0 branch. Accessing xgboost.readthedocs.io should redirect to the release branch automatically.

[david-cortes]

It was replaced by the release_3.0.0 branch. Accessing xgboost.readthedocs.io should redirect to the release branch automatically.

That's quite problematic if one wants to link to "docs of a class/function in last XGB release" elsewhere.

Most other libraries have a 'stable' tag, which for example can be used with intersphinx in docs of other libraries that link to some xgboost function or class. Granted, it could be replaced with 'latest', but users of public releases typically would want to look at 'stable' instead.

[trivialfis]

I need to figure out a way to create a stable tag on read the docs and redirect it to release_3.0.0. Previously XGBoost set up a stable git branch, which I couldn't easily update to release_3.0.0 (without force push or remove/recreate).

[trivialfis]

Opened an issue there: readthedocs/readthedocs.org#12081 .

[hcho3]

By default, RTD uses the latest tag, not the latest branch, as stable.

[trivialfis]

I re-activated the stable RTD, it's using 2.1.4 tag instead of 3.0.0. @hcho3 Do you know of a way to make it track the release_3.0.0 branch?