Ship logo and favicon with docs, to make them self-contained

[SimonSapin]

When looking at local docs shipped with my compiler in share/doc/rust/html, my browser makes requests to the internet:

• http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png
• https://doc.rust-lang.org/favicon.ico

These requests are sometimes slow, and seem to block rendering. These files should be shipped together with the docs so that rendering local docs is always fast.

CC @alexcrichton

[alexcrichton]

Sounds like a fine idea to me.

[steveklabnik]

https://gist.github.com/steveklabnik/90ab0bb475bfd7cba236 would be helpful :)

[SimonSapin]

Trying now with data URLs

[SimonSapin]

Alternative idea: when the string’s value in #![doc(html_logo_url = "...")] is not an absolute URL (i.e. doesn’t match ^[a-zA-Z0-9+.-]+:), have rustdoc interpret it as a file name relative to the source file (like include_bin!), copy that file somewhere into target/doc/, and fix up the URL when it’s being used to have the right number of ../ components, like for main.css.

[alexcrichton]

I think it'd be fine to just check in these assets and then have the build system ensure they move along to the right location, the crates could then just change the URL for the favicon/logo as they'll be hosted on doc.rust-lang.org

[llogiq]

I think @SimonSapin is on the right track – perhaps it'd be good to have a %ROOT (or some such) wildcard that inserts the right number of "../" according to the current URL. Relative URLs will work even if the source files are moved around.

[steveklabnik]

Triage: no change

[GuillaumeGomez]

I'll fix it.

[GuillaumeGomez]

Fixed by #57552.

[SimonSapin]

And #58185