Open to add closed for update

[ArvindGundimajalu]

I am looking for a feature that allows me to lockdown updates to files. Essentially making them immutable.
This will be really handy for files that define interface, allowing to control the possibility of a breaking change getting introduced.
The feature needs to operate at 2 levels

1. File level - allowing to lock specific files.
2. Folder level - allowing to lock all files under a specific path.

The feature should now block a user from adding new files. But once added it should not be possible to update or delete the file without special privileges.