Two identical filenames in one directory!

[Guy Harris]

>1) In both V6 and V7, root is able to write a newly creat()'ed directory.
>   This is how mkdir used to make the . and .. entries.

Wrongo.  "mkdir" made those entries with the "link" system call.

In any case, UNIX never let user-mode programs running as root open a
directory for writing, even if bugs caused it not to properly check
whether "core" was a directory.