DOC: Redirect old whatsnew links

In https://github.com/pandas-dev/pandas/pull/21599 we’re chagning the structure of our whatsnew. Previously the whatsnew for each version was concatenated into a single large file.

Consider a link to the anchor #whatsnew-0190-enhancements-other. There are three cases:

1. Version-specific URLs like http://pandas.pydata.org/pandas-docs/version/0.23.0/whatsnew.html#whatsnew-0190-enhancements-other will continue to work. We don’t have to change anything.
2. People linking via /stable (which is probably more common), or to version 0.24.0 or higher will break. http://pandas.pydata.org/pandas-docs/stable/whatsnew.html#whatsnew-0190-enhancements-other won’t be a valid reference. We would need to rewrite it to http://pandas.pydata.org/pandas-docs/stable/releases/#whatsnew-0190-enhancements-other

We use nginx for our webserver at pandas.pydata.org. But AFAICT, we can’t use a rewrite rule to redirect this links, since nginx doesn’t see the anchor.

We should be able to detect this in Javascript. When we’re on the whatsnew for 0.24.0 or greater, we want to look for anchors pointing to /whatsnew.html#whatsnew-<version> for 0.23.4 or older. Then we’d rewrite /whatsnew.html#whatsnew-<version>-<title> to /whatsnew/<version>.html#<title>. So a test case is

before: http://pandas.pydata.org/pandas-docs/stable/whatsnew.html#whatsnew-0190-enhancements-other
after:  http://pandas.pydata.org/pandas-docs/stable/whatsnew/v0.19.0.html#other-enhancements

[westurner]

Thanks for this! A redirect map with a hook for parsing uri fragments could be a useful addition to Sphinx, as well.

You can add custom JavaScript to Sphinx templates with add_js_file() (was: add_javascript()) in conf.py.

https://www.sphinx-doc.org/en/master/extdev/appapi.html#sphinx.application.Sphinx.add_js_file

https://docs.readthedocs.io/en/latest/guides/adding-custom-css.html#adding-custom-css-or-javascript-to-a-sphinx-project

[TomAugspurger]

Just merged it into master, so you you merge that then you’re good to go.

FYI, the doc build will be live in ~1 hour, whenever https://travis-ci.org/pandas-dev/pandas/jobs/455198927 finishes. Those will be uploaded to http://pandas-docs.github.io/pandas-docs-travis/ (you don’t have to worry about redirecting anything on that domain)