feat!: add flags-dir base flag (#519)

BREAKING CHANGE: SfCommand.baseFlags may cause compilation errors

messages/messages.md

@@ -112,3 +112,7 @@ Found duplicate argument %s.
 # warning.arrayInputFormat
 
 The input format for array arguments has changed. Use this format: --array-flag value1 --array-flag value2 --array-flag value3
+
+# flags.flags-dir.summary
+
+Import flag values from a directory.

src/sfCommand.ts

@@ -5,7 +5,7 @@
  * For full license text, see LICENSE.txt file in the repo root or https://opensource.org/licenses/BSD-3-Clause
  */
 import os from 'node:os';
-import { Command, Config, HelpSection } from '@oclif/core';
+import { Command, Config, HelpSection, Flags } from '@oclif/core';
 import {
   envVars,
   Messages,
@@ -122,6 +122,13 @@ export abstract class SfCommand<T> extends Command {
    */
   public static errorCodes?: HelpSection;
 
+  public static baseFlags = {
+    'flags-dir': Flags.directory({
+      summary: messages.getMessage('flags.flags-dir.summary'),
+      helpGroup: 'GLOBAL',
+    }),
+  };
+
   /**
    * Set to true if the command must be executed inside a Salesforce project directory.
    *