All of the old guide stubs have broken links to the new book

[camjackson]

Example: https://github.com/rust-lang/rust/blob/master/src/doc/guide-crates.md

I was going to fix them all myself, but I wasn't sure of the right change. It seems to me that all of the links that are to book/topic.html should be pointing to trpl/topic.md? Is that right?

[steveklabnik]

They link correctly when generated, but not when in GitHub. Can't make both work in every case, I don't think.