[karmakaze]

The DEC VMS operating system had an extra component to their filenames. It was name.ext;version where the 'version' was an integer that incremented. Normally you would see the last N versions on any modified files until you purged them and then you'd only have one and the version numbers would start over.

When a program read a file it wouldn't say which version and the most recent would be read, or the next version written.

You could use a special filesystem that worked like this.

Edit: searching 'filesystem for git' has some matches.