packages/cli/src/commands/upgrade/legacyUpgrade.js
function upgradeProjectFiles(projectDir, projectName) {
  // Just overwrite
  copyProjectTemplateAndReplace(
    path.dirname(require.resolve('react-native/template')),
    projectDir,
    projectName,
    {upgrade: true},
  );
}
function upgradeProjectFiles(projectDir, projectName) {
  // Just overwrite
  copyProjectTemplateAndReplace(
    path.dirname(require.resolve('react-native/template')),
    projectDir,
    projectName,
    {upgrade: true},
  );
}
function upgradeProjectFiles ( projectDir , projectName ) { // Just overwrite copyProjectTemplateAndReplace ( path . dirname ( require . resolve ( 'react-native/template' ) ) , projectDir , projectName , { upgrade : true } , ) ; }
Once all checks passed, upgrade the project files.
Once all checks passed upgrade the project files .