php.internals: Changes to Git commit workflow

Hi everyone, Yesterday (2021-03-28) two malicious commits were pushed to the php-src repo [1] from the names of Rasmus Lerdorf and myself. We don't yet know how exactly this happened, but everything points towards a compromise of the git.php.net server (rather than a compromise of an individual git account). While investigation is still underway, we have decided that maintaining our own git infras