Only a minority of programs need that functionality. Databases and everything which implements transactions or version control itself, certainly don't. Neither all the temporary files, e.g. a compiler creates. If version control of your configuration files is external to the host (e.g. if some configuration management system like puppy, chef, etc. is used) then it's get in the way as well.

Dave Cutler was wearing his marketing hat when he claimed that such functionality belongs in the file system code. It would be nice, if it were in a library all interested applications could easily link to though.

I essentially have versions for all my files because of Apple’s “Time Machine” backup system. There’s the external drive at my desk and there’s also the cache of recent changes it maintains in free space on the local drive.

Both of these have saved my ass in the past. I don’t care if it’s actually part of the file system, but it sure as hell belongs somewhere in the OS IMHO.

> Databases and everything which implements transactions or version control itself, certainly don't.

Why should programs implement these themselves? It should be part of the OS.

I don't think you can get Oracle, IBM, etc. to agree on how a database ought to be implemented. It clearly depends on the use case as well. More fundamentally one can argue, that what can be implemented in userspace ought to be implemented in userspace (for security and maintenance reasons alone), rather than the kernel. And what good does a db do in a compute node?