first commit

app_vue/node_modules/@vue/cli-plugin-babel/migrator/index.js

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+const { chalk } = require('@vue/cli-shared-utils')
+
+module.exports = api => {
+  api.transformScript(
+    'babel.config.js',
+    require('../codemods/usePluginPreset')
+  )
+
+  if (api.fromVersion('^3')) {
+    api.extendPackage(
+      {
+        dependencies: {
+          'core-js': '^3.8.3'
+        }
+      },
+      { warnIncompatibleVersions: false }
+    )
+
+    // TODO: implement a codemod to migrate polyfills
+    api.exitLog(`core-js has been upgraded from v2 to v3.
+If you have any custom polyfills defined in ${chalk.yellow('babel.config.js')}, please be aware their names may have been changed.
+For more complete changelog, see https://github.com/zloirock/core-js/blob/master/CHANGELOG.md#300---20190319`)
+  }
+}