fix(ncu-config): support encrypted config in ncu-config (#964)

This otherwise always re-write the config into ~/.ncurc instead of
~/.ncurc.gpg

Author: joyeecheung

lib/config.js

@@ -2,7 +2,7 @@ import path from 'node:path';
 import os from 'node:os';
 
 import { readJson, writeJson } from './file.js';
-import { existsSync } from 'node:fs';
+import { existsSync, mkdtempSync, rmSync } from 'node:fs';
 import { spawnSync } from 'node:child_process';
 
 export const GLOBAL_CONFIG = Symbol('globalConfig');
@@ -61,13 +61,31 @@ export function getConfigPath(configType, dir) {
 };
 
 export function writeConfig(configType, obj, dir) {
-  writeJson(getConfigPath(configType, dir), obj);
+  const configPath = getConfigPath(configType, dir);
+  const encryptedConfigPath = configPath + '.gpg';
+  if (existsSync(encryptedConfigPath)) {
+    const tmpDir = mkdtempSync(path.join(os.tmpdir(), 'ncurc-'));
+    const tmpFile = path.join(tmpDir, 'config.json');
+    try {
+      writeJson(tmpFile, obj);
+      const { status } = spawnSync('gpg',
+        ['--default-recipient-self', '--yes', '--encrypt', '--output', encryptedConfigPath, tmpFile]
+      );
+      if (status !== 0) {
+        throw new Error('Failed to encrypt config file: ' + encryptedConfigPath);
+      }
+    } finally {
+      rmSync(tmpDir, { recursive: true, force: true });
+    }
+    return encryptedConfigPath;
+  }
+  writeJson(configPath, obj);
+  return configPath;
 };
 
 export function updateConfig(configType, obj, dir) {
   const config = getConfig(configType, dir);
-  const configPath = getConfigPath(configType, dir);
-  writeJson(configPath, Object.assign(config, obj));
+  writeConfig(configType, Object.assign(config, obj), dir);
 };
 
 export function getHomeDir(home) {