cli: document --inspect port 0 behavior

PR-URL: nodejs#53782
Reviewed-By: Kohei Ueno <[email protected]>

doc/api/cli.md

@@ -1452,7 +1452,8 @@ or poisoning attack. Avoid using this option.
 added: v6.3.0
 -->
 
-Activate inspector on `host:port`. Default is `127.0.0.1:9229`.
+Activate inspector on `host:port`. Default is `127.0.0.1:9229`. If port `0` is
+specified, a random available port will be used.
 
 V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug
 and profile Node.js instances. The tools attach to Node.js instances via a
@@ -1486,7 +1487,8 @@ added: v7.6.0
 -->
 
 Activate inspector on `host:port` and break at start of user script.
-Default `host:port` is `127.0.0.1:9229`.
+Default `host:port` is `127.0.0.1:9229`. If port `0` is specified,
+a random available port will be used.
 
 See [V8 Inspector integration for Node.js][] for further explanation on Node.js debugger.
 
@@ -1499,7 +1501,8 @@ added: v7.6.0
 Set the `host:port` to be used when the inspector is activated.
 Useful when activating the inspector by sending the `SIGUSR1` signal.
 
-Default host is `127.0.0.1`.
+Default host is `127.0.0.1`. If port `0` is specified,
+a random available port will be used.
 
 See the [security warning][] below regarding the `host`
 parameter usage.
@@ -1520,7 +1523,8 @@ added:
 -->
 
 Activate inspector on `host:port` and wait for debugger to be attached.
-Default `host:port` is `127.0.0.1:9229`.
+Default `host:port` is `127.0.0.1:9229`. If port `0` is specified,
+a random available port will be used.
 
 See [V8 Inspector integration for Node.js][] for further explanation on Node.js debugger.