As a follow up from #295

Most deployment setups für TYPO3 CMS (including TYPO3 Surf) install extensions via install:generatepackagestates and extension:setupactive.
As a minor flaw this does not emit the TYPO3\CMS\Extensionmanager\Utility\InstallUtility::afterExtensionInstall signal like extension:activate does for each package.

I'm not 100% convinced it's save to trigger the event by default as it would be emitted on every deploy. Maybe there are extensions that use the signal and rely on the "actual" one-time extension install situation. So as a workaround the behaviour could be enabled by passing a flag to the extension:setupactive command:

public function setupActiveCommand($force = FALSE)
{
    $active_packages = $this->packageManager->getActivePackages();
    $this->setupExtensions($active_packages, $force ? array_keys($active_packages) : []);
}

The setupCommand should receive this new flag as well.

On the other hand it could also become the default behaviour... I think all slots using this signal must be idempotent as you can uninstall and reinstall an extension with the extension-manager as well.