add root book as a landing page

[hydrolarus]

This also adds a robots.txt so that PR previews don't get indexed by search engines.

Also deduplicates the theme in the repository using symlinks. They will still be duplicated once deployed, but that should be okay.

[github-actions]

Thank you for your PR! A preview of your changes is live at
https://docs.clash-lang.org/pr/14/

[DigitalBrains1]

This currently runs:

mdbook build
mkdir -p public/pr
cp CNAME public/
cp robots.txt public/
mkdir -p public
git fetch --depth=1 origin +gh-pages:refs/remotes/origin/gh-pages
git archive --prefix=public/ refs/remotes/origin/gh-pages -- ':(glob)pr-*/**' | tar x || true

So:

• mdbook build will create the directory public
• mkdir -p public/pr will create the directories public and public/pr
• mkdir -p public will create the directory public
• tar x will create the directories public, public/pr and many more, unless there is no open PR; it doesn't create any dirs then.

I think the cps can just fail and abort CI if mdbook build did not create the public directory. Something is very wrong then, and it should abort. Note that the cps are very explicitly "copy to this directory"; if the directory doesn't exist, cp does an error exit.

If you don't like that, please just do

mdbook build
mkdir -p public
cp CNAME public/
cp robots.txt public/
git fetch --depth=1 origin +gh-pages:refs/remotes/origin/gh-pages
git archive --prefix=public/ refs/remotes/origin/gh-pages -- ':(glob)pr-*/**' | tar x || true

because it's a bit much :-D.

Note that there's another issue with that code, see message below.

[DigitalBrains1]

You forgot to adjust the glob for git archive

[DigitalBrains1]

Thanks for going forward with this!

[hydrolarus]

Thanks for the review! I kept the mkdir -p public/pr just because it makes me feel better when the PR build action uses ./pr as a destination dir to publish.

[hydrolarus]

cleaned up the directory creation even more! Should be good now?

[DigitalBrains1]

Do you mind if I squash the latest commit into the "add root book" commit? I like clean histories :-D

[hydrolarus]

No no, go ahead if you want to do it :)