Add "How to build documentation" section.

[XAMPPRocky]

It'd be helpful for people who want make documentation pull requests that aren't just typo's to be able to build the documentation, and preview it themselves. Adding a "How To" about how documentation for the main repo should be built, would be helpful.

[TimNN]

Building the documentation should be as simple as make docs, which however requires a full rust build which can take some time. Once a full build has been completed make docs NO_REBUILD=1 should allow you to build the documentation without rebuilding the whole compiler. I don't think there currently is a way to build the docs without building the compiler.

Edit: Running make tips gives a very basic introduction to rust's build system.

[steveklabnik]

I don't think there currently is a way to build the docs without building the compiler.

You can run rustdoc on any crate, so I often rustdoc --test src/libcore/lib.rs or whatever I'm working on. It works on markdown files too.

[tomjakubowski]

You can run rustdoc on any crate, so I often rustdoc --test src/libcore/lib.rs or whatever I'm working on. It works on markdown files too.

It's worth noting that you need a (very) recent version of rustdoc to create docs from the source in master HEAD. It's often the case that even a nightly rustdoc is not new enough (although maybe it is, if you pass --cfg stage0 or something...).

[steveklabnik]

Huh, I've never ran into that as an issue.