Re: file-name-shadow-mode

[Richard Stallman]

    But actually, I think my proposal about a C level interface into
    substitute-in-file-name would be most efficient, robust and
    unproblematic in the long run, and possibly useful for other
    applications as well.

I don't want to do this, because it puts too much complexity in a
place where it could cause trouble.  I'd rather just stay away from it.

To duplicate just the parsing aspect of substitute-in-file-name
for this one purpose would be better.