Add hosted_on variable for a link in the footer

[hugovk]

Helps python/docs-community#5.

If hosted_on is defined in your docs' conf.py:

html_theme_options= {
'collapsiblesidebar': True,
'hosted_on': '<a href="https://example.com">Example</a>',
'issues_url': '/bugs.html',
'license_url': '/license.html',
'root_include_title': False# We use the version switcher instead.
}

Adds a "Hosted by" line to the footer:

Conditional

For python/docs-community#5, we can instead add this in conf.py:

ifos.getenv("READTHEDOCS"):
html_theme_options["hosted_on"] ='<a href="https://about.readthedocs.com/">Read the Docs</a>'

And we'll only get the "Hosted by" line for builds created on Read the Docs:

Here's a demo build:

• https://hugovk-cpython.readthedocs.io/en/hosted-on/
• https://github.com/hugovk/cpython/tree/hosted-on

If you build that locally or on another server which doesn't have the env var defined, we don't get the link:

[willingc]

Looks good to me. Thanks @hugovk

[hugovk]

This has now been released, so here's the follow-up: python/cpython#114697