I am currently looking forward to work with a bare git repository in order to deploy on a production server, i have a "post-receive" hook who use git checkout to update the production folder. The application is a PHP Website.
In fact i'm wondering if it is absolutely safe to push on a production server with git while there is someone using the web-app, does git update the file in a transaction-like way by locking every update files or is he working files by files ? Is it possible that the user load the page and have the CSS of the old commit but the PHP of the new one ? (if he's very unlucky)
TL;DR : Is there any risk to push while people use the website ?
Sorry for my english ! Thanks for your help !