Add tracking issue and unstable documentation

Author: willcrichton

src/bin/cargo/commands/doc.rs

@@ -84,10 +84,9 @@ pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     };
 
     if compile_opts.rustdoc_scrape_examples.is_some() {
-        // FIXME(wcrichto): add a tracking issue once this gets merged and add issue number below
         config
             .cli_unstable()
-            .fail_if_stable_opt("--scrape-examples", 0)?;
+            .fail_if_stable_opt("--scrape-examples", 9910)?;
     }
 
     let doc_opts = DocOptions {

src/doc/src/reference/unstable.md

@@ -1207,7 +1207,7 @@ for the appropriate target and influenced by any other RUSTFLAGS.
 * Tracking Issue: [#9778](https://github.com/rust-lang/cargo/issues/9778)
 * PR: [#9627](https://github.com/rust-lang/cargo/pull/9627)
 
-The `different-binary-name` feature allows setting the filename of the binary without having to obey the 
+The `different-binary-name` feature allows setting the filename of the binary without having to obey the
 restrictions placed on crate names. For example, the crate name must use only `alphanumeric` characters
 or `-` or `_`, and cannot be empty.
 
@@ -1378,7 +1378,23 @@ The 2021 edition has been stabilized in the 1.56 release.
 See the [`edition` field](manifest.md#the-edition-field) for more information on setting the edition.
 See [`cargo fix --edition`](../commands/cargo-fix.md) and [The Edition Guide](../../edition-guide/index.html) for more information on migrating existing projects.
 
+
 ### Custom named profiles
 
 Custom named profiles have been stabilized in the 1.57 release. See the
 [profiles chapter](profiles.md#custom-profiles) for more information.
+
+
+### scrape-examples
+
+* RFC: [#3123](https://github.com/rust-lang/rfcs/pull/3123)
+* Tracking Issue: [#9910](https://github.com/rust-lang/cargo/issues/9910)
+
+The `--scrape-examples` argument to the `doc` command tells Rustdoc to search
+crates in the current workspace for calls to functions. Those call-sites are then
+included as documentation. The flag can take an argument of `all`, `lib`, or `examples`
+which configures which crate in the workspace to analyze for examples. For instance:
+
+```
+cargo doc --scrape-examples examples -Z unstable-options
+```