feat(xo-cli): --json flag

Fixes #6736

packages/xo-cli/index.mjs

@@ -259,9 +259,12 @@ const help = wrap(
     <property>=<value>
       Restricted displayed objects to those matching the patterns.
 
-  $name <command> [<name>=<value>]...
+  $name <command> [--json] [<name>=<value>]...
     Executes a command on the current XO instance.
 
+    --json
+      Prints the result in JSON format.
+
 $name v$version`.replace(/<([^>]+)>|\$(\w+)/g, function (_, arg, key) {
       if (arg) {
         return '<' + chalk.yellow(arg) + '>'
@@ -449,6 +452,11 @@ function ensurePathParam(method, value) {
 }
 
 async function call(args) {
+  const jsonOutput = args[1] === '--json'
+  if (jsonOutput) {
+    args.splice(1, 1)
+  }
+
   if (!args.length) {
     throw new Error('missing command name')
   }
@@ -518,7 +526,7 @@ async function call(args) {
       }
     }
 
-    return result
+    return jsonOutput ? JSON.stringify(result, null, 2) : result
   } finally {
     await xo.close()
   }