Sort feature list

Author: Jon Gjengset

src/cargo/core/features.rs

@@ -545,39 +545,42 @@ impl Features {
 #[derive(Default, Debug, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]
 pub struct CliUnstable {
-    pub print_im_a_teapot: bool,
+    // Permanently unstable features:
     pub allow_features: Option<BTreeSet<String>>,
+    pub print_im_a_teapot: bool,
 
-    pub unstable_options: bool,
-    pub no_index_update: bool,
-    pub avoid_dev_deps: bool,
-    pub minimal_versions: bool,
+    // All other unstable features.
+    // Please keep this list lexiographically ordered.
     pub advanced_env: bool,
-    pub config_include: bool,
-    pub dual_proc_macros: bool,
-    pub mtime_on_use: bool,
-    pub named_profiles: bool,
+    pub avoid_dev_deps: bool,
     pub binary_dep_depinfo: bool,
     #[serde(deserialize_with = "deserialize_build_std")]
     pub build_std: Option<Vec<String>>,
     pub build_std_features: Option<Vec<String>>,
-    pub timings: Option<Vec<String>>,
-    pub doctest_xcompile: bool,
+    pub config_include: bool,
+    pub configurable_env: bool,
+    pub credential_process: bool,
     pub doctest_in_workspace: bool,
-    pub panic_abort_tests: bool,
-    pub jobserver_per_rustc: bool,
+    pub doctest_xcompile: bool,
+    pub dual_proc_macros: bool,
+    pub enable_future_incompat_feature: bool,
+    pub extra_link_arg: bool,
     pub features: Option<Vec<String>>,
-    pub separate_nightlies: bool,
+    pub jobserver_per_rustc: bool,
+    pub minimal_versions: bool,
+    pub mtime_on_use: bool,
     pub multitarget: bool,
+    pub named_profiles: bool,
+    pub namespaced_features: bool,
+    pub no_index_update: bool,
+    pub panic_abort_tests: bool,
+    pub patch_in_config: bool,
     pub rustdoc_map: bool,
+    pub separate_nightlies: bool,
     pub terminal_width: Option<Option<usize>>,
-    pub namespaced_features: bool,
+    pub timings: Option<Vec<String>>,
+    pub unstable_options: bool,
     pub weak_dep_features: bool,
-    pub extra_link_arg: bool,
-    pub patch_in_config: bool,
-    pub credential_process: bool,
-    pub configurable_env: bool,
-    pub enable_future_incompat_feature: bool,
 }
 
 const STABILIZED_COMPILE_PROGRESS: &str = "The progress bar is now always \