Shopware\Plugin\Services\Checkout::updatePlugin PHP Method

    private function updatePlugin($branch, $absPath, $pluginName)
    {
        $this->ioService->writeln("Plugin is already installed");
        $this->utilities->changeDir($absPath);
        $this->gitUtil->run("fetch --progress origin");
        $output = $this->gitUtil->run("log HEAD..origin/master --oneline");
        if (trim($output) === '') {
            $this->ioService->writeln("Plugin '{$pluginName}' is up to date");
            if ($branch) {
                $this->gitUtil->run("checkout {$branch}");
            }
            return;
        }
        $this->ioService->writeln("Incoming changes:");
        $this->ioService->writeln($output);
        $this->gitUtil->run("reset --hard HEAD");
        $this->gitUtil->run("pull");
        if ($branch) {
            // the CWD change is a fix for older versions of GIT which do not support the -C flag
            $cwd = getcwd();
            $this->utilities->changeDir($absPath);
            $this->gitUtil->run("checkout {$branch}");
            $this->utilities->changeDir($cwd);
        }
        $this->ioService->writeln("Plugin '{$pluginName}' successfully updated.\n");
        return;
    }