🚀 go-pugleaf

We seem to have an inconsistency ahead of us.  Like this:

The Unix Time-Sharing System:
	As another limiting case, the null file name refers to the
	current directory...

Unix 3.0 INTRO(2):
	Unless specifically stated otherwise, the null path name is
	treated as if it named a non-existent file...

I can't find any places in the 3.0 manual where anything is "specifically
stated otherwise".

What to do?  I am ambivalent about this one.  There is something to be
said for the V7 interpretation, although the do-something-reasonable-for-
strange-input principle is weaker for system calls than for programs that
users invoke directly.  On the other hand, objecting to null filenames
would have caught a number of bugs I've seen at one time or another.
Note that the -1 pointer points to a null filename in V7.  So does
the NULL pointer if you are running split-space.  On the whole, I think
any use of a null filename is likely to be the result of a bug, so it
should be trapped.

In practice, the 3.0 interpretation will probably triumph by sheer
weight of numbers.