[tex-k] TeX finding filenames with spaces

[Karl Berry]

    I don't see any essential difference between \input with optional braces,
    and \input with optional quotes.

I suppose not, technically.  But I still think quotes are better,
because 1) braces are special to TeX and using optional braces to
delimit the filename seems like a great source of confusion, and 2)
fpTeX and MikTeX already use quotes.  Why be gratitiously incompatible
with existing practice?

    But, why not lean toward whatever mechanism is used for outputting
    special characters in \special{} and \write{} and \message{}?

Because people want to say \input "foo bar" and not have to mess around
with getting a special space expanded in their filename?  They just want
it to work.  That's my understanding anyway.