Add doc notes on how to depend on '-dev' versions.

core/lib/src/lib.rs

@@ -43,8 +43,13 @@
 //! rocket = "0.5.0-dev"
 //! ```
 //!
-//! See the [guide](https://rocket.rs/master/guide) for more information on how to
+//! <small>Note that development versions, tagged with `-dev`, are not published
-//! write Rocket applications. Here's a simple example to get you started:
+//! and will will need to be specified as [git dependencies].</small>
+//!
+//! See the [guide](https://rocket.rs/master/guide) for more information on how
+//! to write Rocket applications. Here's a simple example to get you started:
+//!
+//! [git dependencies]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-dependencies-from-git-repositories
 //!
 //! ```rust,no_run
 //! #[macro_use] extern crate rocket;

site/guide/2-getting-started.md

@@ -46,6 +46,19 @@ Now, add Rocket as a dependency in your `Cargo.toml`:
 rocket = "0.5.0-dev"
 ```
 
+! warning: Development versions must be _git_ dependencies.
+
+  Development versions, tagged with `-dev`, are not published. To depend on a
+  development version of Rocket, you'll need to point `Cargo.toml` to a Rocket
+  git repository. For example, with `######` replaced with a git commit hash:
+
+  `
+  [dependencies]
+  `
+  `
+  rocket = { git = "https://github.com/SergioBenitez/Rocket", rev = "######" }
+  `
+
 Modify `src/main.rs` so that it contains the code for the Rocket `Hello, world!`
 program, reproduced below: