The Sphinx documentation only needs access to a relatively small number
of files in the repo in order to be generated. It is a good candidate
for using sparse profiles.
This commit defines and uses a "sphinx-docs" sparse profile containing
only the files relevant to Sphinx documentation generation.
There are some quirks with the profile:
* All moz.build files are included. This bloats the profile
by >1000 files. Worse, it realizes directories that have no business
being realized. This clutters the checkout and makes it harder to
find things. There is a moz.build reader that knows how to retrive
file data from Mercurial. We could use that. This feels like follow-up
fodder.
* All mach_commands.py files are included. `mach help` says you can do
things that you aren't able to do in the sparse checkout. There isn't
a good way to add all *.py files while excluding mach_commands.py
files. We /could/ do it with regular expressions. But those are slow.
Let's leave it as is for now and come up with a better solution later.
MozReview-Commit-ID: 7yiqGGE1nAh
