For a long time, the docs have generated a huge, static HTML package list. It has some
disadvantages:
* It's slow to load
* It's slow to build
* It's hard to search
We now have a nice website that can tell us about Spack packages, and it's searchable so
users can easily find the one or two packages out of 7400 that they're looking for. We
should link to this instead of including a static package list page in the docs.
- [x] Replace package list link with link to packages.spack.io
- [x] Remove `package_list.html` generation from `conf.py`.
- [x] Add a new section for "Links" to the docs.
- [x] Remove docstring notes from contribution guide (we haven't generated RST
for package docstrings for a while)
- [x] Remove referencese to `package-list` from docs.
* docs: add a spack environment for building the docs
* docs: remove tutorial and link to spack-tutorial.readthedocs.io
The tutorial now has its own standalone website, versioned by instances
of the tutorial. Link to that instead of versioning it directly with Spack.
- Generating the HTML from for >2300 packages from RST in Sphinx seems to
take forever.
- Add an option to `spack list` to generate straight HTML instead.
- This reduces the doc build time to about a minute (from 5 minutes on a mac laptop).
