Introduce _getCommandAndAncestors()

Replaces getCommandAndParents():
- turned into an instance method
- used "ancestors" instead of "parents" because it is more specific and
  to avoid confusion with the recently introduced parents array

lib/command.js

@@ -122,6 +122,19 @@ class Command extends EventEmitter {
     return this;
   }
 
+  /**
+   * @returns {Command[]}
+   * @api private
+   */
+
+  _getCommandAndAncestors() {
+    const result = [];
+    for (let command = this; command; command = command.parent) {
+      result.push(command);
+    }
+    return result;
+  }
+
   /**
    * Define a command.
    *
@@ -853,7 +866,7 @@ Expecting one of '${allowedValues.join("', '")}'`);
   getOptionValueSourceWithGlobals(key) {
     // global overwrites local, like optsWithGlobals
     let source;
-    getCommandAndParents(this).forEach((cmd) => {
+    this._getCommandAndAncestors().forEach((cmd) => {
       if (cmd.getOptionValueSource(key) !== undefined) {
         source = cmd.getOptionValueSource(key);
       }
@@ -1256,7 +1269,7 @@ Call on top-level command instead`);
   _chainOrCallHooks(promise, event) {
     let result = promise;
     const hooks = [];
-    getCommandAndParents(this)
+    this._getCommandAndAncestors()
       .reverse()
       .filter(cmd => cmd._lifeCycleHooks[event] !== undefined)
       .forEach(hookedCommand => {
@@ -1627,7 +1640,7 @@ Call on top-level command instead`);
    */
   optsWithGlobals() {
     // globals overwrite locals
-    return getCommandAndParents(this).reduce(
+    return this._getCommandAndAncestors().reduce(
       (combinedOptions, cmd) => Object.assign(combinedOptions, cmd.opts()),
       {}
     );
@@ -2072,7 +2085,7 @@ Call on top-level command instead`);
     }
     const context = this._getHelpContext(contextOptions);
 
-    getCommandAndParents(this).reverse().forEach(command => command.emit('beforeAllHelp', context));
+    this._getCommandAndAncestors().reverse().forEach(command => command.emit('beforeAllHelp', context));
     this.emit('beforeHelp', context);
 
     let helpInformation = this.helpInformation(context);
@@ -2086,7 +2099,7 @@ Call on top-level command instead`);
 
     this.emit(this._helpLongFlag); // deprecated
     this.emit('afterHelp', context);
-    getCommandAndParents(this).forEach(command => command.emit('afterAllHelp', context));
+    this._getCommandAndAncestors().forEach(command => command.emit('afterAllHelp', context));
   }
 
   /**
@@ -2229,18 +2242,4 @@ function incrementNodeInspectorPort(args) {
   });
 }
 
-/**
- * @param {Command} startCommand
- * @returns {Command[]}
- * @api private
- */
-
-function getCommandAndParents(startCommand) {
-  const result = [];
-  for (let command = startCommand; command; command = command.parent) {
-    result.push(command);
-  }
-  return result;
-}
-
 exports.Command = Command;