Git 27 changes

[chadwcarlson]

What needs to be documented?

• https://docs.platform.sh/integrations/source/github.html#source-of-truth: It isn't possible to push to P.sh in this case.
• https://docs.platform.sh/development/variables/use-variables.html#use-provided-variables, adds the PLATFORM_VENDOR variable (platformsh/upsun; avail Build but not Runtime) - to change the behavior of the build according to the vendor.
• "that made possible to restore a backup with more disk than the current disk of the environment needs documentation, but I can't find the page"

Additional context

No response