bug#24117: 25.1; url-http-create-request: Multibyte text in HTTP request

[Dmitry Gutov <dgutov@yandex.ru>]

On 08/09/2016 05:50 PM, Eli Zaretskii wrote:

>> You can't encode it properly without parsing it first.
>
> You don't say what you meant by "encode properly".  It's just a
> string, and there are ways to make a string unibyte without any
> parsing.

Different parts of an URL are supposed to be encoded in different ways.

For instance,

   http://банки.рф/фыва/

turns into

   http://xn--80abwho.xn--p1ai/%D1%84%D1%8B%D0%B2%D0%B0/

The domain is encoded with IDNA, whereas the path uses percent-encoding. 
And they're also often encoded separately (e.g. when you copy-paste the 
above URL from Firefox to a text editor, the result is 
http://банки.рф/%D1%84%D1%8B%D0%B2%D0%B0/).

So I think the encoding of the URL parts should be performed inside 
url-http-create-request. On the master branch, host is passed through 
IDNA encoding, but real-fname is untouched. On emacs-25, I think we 
should convert both to unibyte.

Not sure encode-coding-string is the way to go (why would we assume 
UTF-8?). Personally, using string-as-unibyte makes more sense (neither 
string should contain any multibyte characters at that point), but I 
defer to the more qualified colleagues.

(Why doesn't (encode-coding-string "aaaa" 'ascii) work?)