deploy.lock

[tamagokun]

While a deploy is running, create a deploy.lock file so that subsequent deploys cannot be happening at the same time.

Things to look out for:

If a deploy fails, will it always be able to remove the deploy.lock file? If it cannot, people will be stuck without being able to deploy.

[tamagokun]

There would need to be a "force" option to override a locked deploy.

[muxx]

You can look at flock. Example code

$flock = new FLock(__CLASS__);
if ($flock->isLocked()) {
    $output->writeln("<error> Command ". $this->getName(). " already running in this system. Kill it or try again later </error>", OutputInterface::VERBOSITY_QUIET);                                                                    
    return -1;
}

which uses class Flock from https://github.com/intaro/pinboard/issues/61#issuecomment-35647379. This realization must unlock file when process failed.