Document new behavior of crates.io with the documentation field of the manifest

diff --git a/src/doc/manifest.md b/src/doc/manifest.md
index 6d6eb51d3ab9a714af24fe9e4fafe0b932e214f0..29ee4026254e021f5e5a1a158f751d2fb3545d0b 100644 (file)
--- a/src/doc/manifest.md
+++ b/src/doc/manifest.md
@@ -41,6 +41,15 @@ building native code. More information can be found in the build script
 build = "build.rs"
 ```
 
+## The `documentation` field (optional)
+
+This field specifies a URL to a website hosting the crate's documentation.
+If no URL is specified in the manifest file, [crates.io][cratesio] will
+automatically link your crate to the corresponding [docs.rs][docsrs] page.
+
+[docsrs]: https://docs.rs/
+[cratesio]: https://crates.io/
+
 ## The `exclude` and `include` fields (optional)
 
 You can explicitly specify to Cargo that a set of [globs][globs] should be