special characters in filenames in error messages

[Karl Berry]

Some months ago we discussed a convention for supporting "special"
characters in filenames ("sources") in error messages.  Our conclusion
then was to support C-style escapes.

I wrote a patch for standards.texi saying as much and sent it to rms.
He rejected it, saying the idea was fine, but that the standards should
give one and only one precise way of specifying each problematic character.

After some additional discussion with the people who brought up the
issue in the first place (cc'd), who wanted to use url's in GNU-style
error messages, my new proposal is to use octal escapes \ooo (and
nothing else).  Specifically:

1) if the first character of the source is a ", the source name extends
   to the next ".  (Including :'s, for example.)
2) within that "...", \ooo is recognized.  For instance, \042=" and \134=\,
   so this weird filename (5 chars):
a:"\b
   would be output in an error message as:
"a:\042\134b":10:some message

This should be about as easy to parse as it can be, and it follows rms's
"one character one specification" rule.

The \ooo convention could be used for any character, but in an 8-bit
clean environment, I believe it is only *required* for " and \.

Before I try again with rms ... objections, suggestions?

karl