auto merge of #10880 : cmr/rust/tut++, r=pnkfelix

Many of them are small. Will squash on request, but I feel like it's easier
for everyone (easier to see and back out individual changes) this way.

Author: bors

doc/rustdoc.md

@@ -0,0 +1,72 @@
+% Rust Documentation
+
+`rustdoc` is the built-in tool for generating documentation. It integrates
+with the compiler to provide accurate hyperlinking between usage of types and
+their documentation. Furthermore, by not using a separate parser, it will
+never reject your valid Rust code.
+
+# Creating Documentation
+
+Documenting Rust APIs is quite simple. To document a given item, we have "doc
+comments":
+
+~~~
+// the "link" crate attribute is currently required for rustdoc, but normally
+// isn't needed.
+#[link(name="universe")];
+#[crate_type="lib"];
+
+//! Tools for dealing with universes (this is a doc comment, and is shown on
+//! the crate index page. The ! makes it apply to the parent of the comment,
+//! rather than what follows).
+
+/// Widgets are very common (this is a doc comment, and will show up on
+/// Widget's documentation).
+pub struct Widget {
+	/// All widgets have a purpose (this is a doc comment, and will show up
+	/// the field's documentation).
+	purpose: ~str,
+	/// Humans are not allowed to understand some widgets
+	understandable: bool
+}
+
+pub fn recalibrate() {
+	//! Recalibrate a pesky universe (this is also a doc comment, like above,
+	//! the documentation will be applied to the *parent* item, so
+	//! `recalibrate`).
+	/* ... */
+}
+~~~
+
+Then, one can run `rustdoc universe.rs`. By default, it generates a directory
+called `doc`, with the documentation for `universe` being in
+`doc/universe/index.html`. If you are using other crates with `extern mod`,
+rustdoc will even link to them when you use their types, as long as their
+documentation has already been generated by a previous run of rustdoc, or the
+crate advertises that its documentation is hosted at a given URL.
+
+The generated output can be controlled with the `doc` crate attribute, which
+is how the above advertisement works. An example from the `libstd`
+documentation:
+
+~~~
+#[doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk.png",
+      html_favicon_url = "http://www.rust-lang.org/favicon.ico",
+      html_root_url = "http://static.rust-lang.org/doc/master")];
+~~~
+
+The `html_root_url` is the prefix that rustdoc will apply to any references to
+that crate's types etc.
+
+rustdoc can also generate JSON, for consumption by other tools, with
+`rustdoc --output-format json`, and also consume already-generated JSON with
+`rustdoc --input-format json`.
+
+# Using the Documentation
+
+The web pages generated by rustdoc present the same logical heirarchy that one
+writes a library with. Every kind of item (function, struct, etc) has its own
+color, and one can always click on a colored type to jump to its
+documentation. There is a search bar at the top, which is powered by some
+javascript and a statically-generated search index. No special web server is
+required for the search.