> If I was designing an OS from scratch, I would be inclined to give every file a single primary name, and then have smart links (rather than hard or symbolic links) to implement secondary names.
That's exactly what Apple did 18 years ago. The Apple filesystems originally didn't support hard links or soft links. In 1992 they introduced "Alias" files, which are a smart softlink. In addition to containing the relative path, absolute path, and volumeid/file inode for locating the original file, they even contain enough information to automatically attempt to re-mount a network filesystem in order to access to original file.
It contains enough duplicate information that it can find an original file either if it's been removed/recreated in place, or if it's been moved to another location (but not both at once).
Unfortunately, aliases are not automatically resolved in the OS, but require apps to resolve them manually. In OSX, the GUI frameworks generally do this for you, but the BSDish tools won't work with aliases at all, just seeing them as a regular file. And OSX now supports traditional unix symlinks and hardlinks too.