Systems were breached, what did you expect would happen?

In such a case any company would go into lockdown and only allow the most essential access to the systems while they examine the vulnerabilities that caused the breach, if new vulnerabilities were introduced by the hackers, etc. This makes remote work all but impossible.
They will also in all likelihood rollout backups from before the breach to get rid of whatever surprises the hackers left behind, wiping all Patch progress since then.

Unless its for post-mortem analysis, the modus-operandi in 2021 is to throw a machine that misbehaves in the garbage and provision a new one.

Anyways, you can do that super easily if you are using a virtualization layer (any cloud provider or Openstack & alternatives for on-prem).

If you are operating on bare-metal, its a little more complicated (you got to reprovision your machine on the same hardware given that it isn't virtualized), but you should still have a setup in place to reprovision a machine fairly quickly.

i would expect development to continue as before
yeah a company would do that you wrote if they want to suicide
why would they wipe all the patch progress?

Because they need to get rid of any backdoors, viruses, etc. the hackers might have left. The only way to be sure is through backups and those will wipe the progress.

The same goes for ransomware that might have removed acces to WIP patch files. Only way out is restoring a backup.

but you can clearly separate the game code development from the rest of the system

No you can't because all kinds of nasty surprises might have been introduced into the patch files. Imagine rolling out a patch containing a ransomware routine to customers. You HAVE to wipe those files.

Check against what?

they surely have a version control system , so just check the latest commits

So they find X files with undocumented changes since the last commit ten days ago, what then? They don't exist in a vacuum, you cannot rollback those files and just keep the rest. So you lose whatever progress might have been made since then.

And the hackers might even have been able to sneak something into one of the commits. So first you have to establish since when unauthorised system access existed. Until then no progress can be made at all. That alone will set back any development progress for weeks. And afterwards you might lose X amount of progress on top.

oh yeah purge everything or this could happen with the technician: https://youtu.be/O7hgjuFfn3A?t=555
imho you watched too many hacking movies

and how can they be sure the previous backup is not already infested?
purge the whole project start with inventing diodes

Or maybe I have been employed by companies that were affected by security breaches/ransomware attacks and am speaking from experience.

i highly doubt that

Well, you're wrong.

No, you roll back EVERYTHING to before the attack. This actually becomes problematic with delayed release bugs because learning the exact time and date of infection is tough. But you don't assume anything is safe and not all changes are so simple to detect. Anything that was on the network is suspect, so they'll likely have lost progress.