Use the first paragraph, instead of cookie-cutter text, for rustdoc descriptions

src/test/rustdoc/description.rs

@@ -0,0 +1,19 @@
+#![crate_name = "foo"]
+//! # Description test crate
+//!
+//! This is the contents of the test crate docstring. It should not show up in the description.
+
+// @matches 'foo/index.html' '//meta[@name="description"]/@content' 'Description test crate'
+
+// @matches 'foo/foo_mod/index.html' '//meta[@name="description"]/@content' 'First paragraph description.'
+/// First paragraph description.
+///
+/// Second paragraph should not show up.
+pub mod foo_mod {
+    pub struct __Thing {}
+}
+
+// @matches 'foo/fn.foo_fn.html' '//meta[@name="description"]/@content' 'Only paragraph.'
+/// Only paragraph.
+pub fn foo_fn() {}
+

src/test/rustdoc/description_default.rs

@@ -0,0 +1,12 @@
+#![crate_name = "foo"]
+
+// @matches 'foo/index.html' '//meta[@name="description"]/@content' 'API documentation for the Rust `foo` crate.'
+
+// @matches 'foo/foo_mod/index.html' '//meta[@name="description"]/@content' 'API documentation for the Rust `foo_mod` mod in crate `foo`.'
+pub mod foo_mod {
+    pub struct __Thing {}
+}
+
+// @matches 'foo/fn.foo_fn.html' '//meta[@name="description"]/@content' 'API documentation for the Rust `foo_fn` fn in crate `foo`.'
+pub fn foo_fn() {}
+