change stable to be a symlink to the latest released version

[mattip]

The idea is to make the stable directory a symlink to the latest released documents, to remove one point of friction when releasing a new version. This is the way numpy does it: the stable symlink seamlessly works with github docs to point to the 1.19.0 docs

This has a merge conflict since the docs are updated every night somehow the stable docs got out of sync?. I will rebase fix it if I can convince the maintainers as to the approach, but then it must be merged before the next nightly build. Edit: Not clear why there is a conflict, the files on my checkout are identical.

The commits to reconstruct this were (on linux where symlinks work)

git checkout site
git pull
git checkout -b stable
cd docs
git rm -r 1.6.0
git commit -m"remove links in 1.6.0"
git mv stable 1.6.0
git commit -m"move stable to 1.6.0"
ln -s 1.6.0 stable
git add stable
git commit -m"recreate stable as a soft link to 1.6.0"
git push

[netlify]

Deploy preview for pytorch-dot-org-preview processing.

Building with commit 38a14e8

https://app.netlify.com/sites/pytorch-dot-org-preview/deploys/5f507fd9e0525a00071e3443

[mattip]

The preview works, stable documents are visible even though they are a symlink.

[zou3519]

This is amazing -- the reason why I put in the redirect pages way back when was because I didn't think github pages would support symlinks. The symlinks are a much cleaner solution and will definitely improve our docs build process

[brianjo]

@mattip Thanks for this PR. I'm having a little trouble fixing the conflict. If you could do so, please feel free to fix and merge. (I can fix the file later if there's a data loss.)

[mattip]

CI is green. I cannot merge (no permissions).

[brianjo]

Awesome! Thanks @mattip!