Stefan Monnier wrote:
>> Here is a patch against EMACS_22_BASE.
>>     
>
> I'd rather use a less arbitrary scheme.  E.g.
> - only accept unchanged safe chars (rather than rule out
>   dangerous ones), e.g. [:alnum:] and maybe a couple more.
> - everything else encoded following quoted-printable.
>
> Of course, QP applies to bytes, not to chars, which also points to
> a potential problem with [:alnum:] since it includes multibyte chars
> which may also be rejected, but I think that would be safe enough for
> a start.
>   

OK, here's a revised patch that accepts only ASCII alphanumerics, -, _, 
., ~, # and +, and percent encodes all others.
It's not strict URL encoding, since multibyte characters will be 
translated to more than two hex characters, but as far as I can tell the 
encoding doesn't have to be reversable, just give unique names that 
don't contain invalid characters, so I think it is good enough. On the 
trunk it is cheap and easy to convert to utf-8, so we could properly URL 
encode them there.