We need to be able to link to configuration attributes, and they
should show up in the index. To that end, add some sphinx
directives to support config objects and attributes. These handle
nesting so that when we get deep into nested yaml (eg,
pipeline.trigger.gerrit.event) the full path will appear in the
header for the attribute. The ancestors will not be as prominent.
This ends up looking like the python class.FUNCTION() headers
in the stdlib docs.
The implementation is based on, and is compatible with, the nascent
zuul-sphinx module. Once that is published, we can either move
this code into that module, or depend on that module and add these
directives to the domain it creates.
The sphinx theme is changed to the current Sphinx default. That
is the theme "alabaster" (note, this is distinct from the theme
named "default", which is the old python2 style theme). Alabaster
has top-notch typography, and most importantly, it renders the
kinds of nested descriptors we're using very well.
Change-Id: I673b20849dd808e8fbff33fa1a7524227d1a6011
1761e8623f