Mark runc features experimental

Follow-up to PR 3296

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

README.md

@@ -301,6 +301,7 @@ WantedBy=multi-user.target
 * [Checkpoint and restore](./docs/checkpoint-restore.md)
 * [systemd cgroup driver](./docs/systemd.md)
 * [Terminals and standard IO](./docs/terminals.md)
+* [Experimental features](./docs/experimental.md)
 
 ## License
 

docs/experimental.md

@@ -0,0 +1,11 @@
+# Experimental features
+
+The following features are experimental and subject to change:
+
+- The `runc features` command (since runc v1.1.0)
+
+The following features were experimental in the past:
+
+Feature                                  | Experimental release | Graduation release
+---------------------------------------- | -------------------- | ------------------
+cgroup v2                                | v1.0.0-rc91          | v1.0.0-rc93

features.go

@@ -20,6 +20,7 @@ var featuresCommand = cli.Command{
 	Description: `Show the enabled features.
    The result is parsable as a JSON.
    See https://pkg.go.dev/github.com/opencontainers/runc/types/features for the type definition.
+   The types are experimental and subject to change.
 `,
 	Action: func(context *cli.Context) error {
 		if err := checkArgs(context, 0, exactArgs); err != nil {

types/features/features.go

@@ -1,4 +1,5 @@
 // Package features provides the JSON structure that is printed by `runc features` (since runc v1.1.0).
+// The types in this package are experimental and subject to change.
 package features
 
 // Features represents the supported features of the runtime.