bug#7617: 24.0.50; `expand-file-name': removal of slashes

[Drew Adams]

> perhaps you run the string through expand-file-name too early,
> before massaging it in some way that gives a valid file name.

I do not want to change the strings into valid file names.
That should be clear by now.

> Or maybe that you should run expand-file-name only on parts
> of the file name, the parts that _are_ valid file names.

That's one possibility, I suppose.  But I'm not really eager to analyze string
inputs to try to discover pieces that might be valid file names for various
operating systems.

And it's not clear what that would mean in terms of the expansion I'm after
(which is exactly the expansion of `expand*' minus the slash collapsing).

But I recognize what you suggest as a possibility.  Likewise, removing any
ignorable prefix temporarily, expanding, and reapplying the prefix.

Such approaches seem messier than what I'm doing now, which at least leverages
`expand*' (for its OS knowledge and expansion function), and then undoes the
slash collapsing.

> Call expand-file-name on parts of a file name, then `concat' them
> together (with any number of slashes that you want)?

See above.  I appreciate your trying to help, however.