Subject: Re: [PATCH] gitweb: handle non UTF-8 text

From: Jakub Narebski <[email-masked]>
Date: Tue, 29 May 2007 11:21:11 +0200

[Cc: authors of git-cvsserver]

On Tue, 29 May 2007, Petr Baudis wrote:
> On Mon, May 28, 2007 at 10:47:34PM CEST, Martin Koegler wrote:

>> gitweb assumes, that everything is in UTF-8. If a text contains invalid
>> UTF-8 character sequences, the text must be in a different encoding.

But it doesn't tell us _what_ is the encoding. For commit messages,
with reasonable new git, we have 'encoding' header if git known that
commit message was not in utf-8.

By the way, I winder why we don't have such header for tag objects
(i18n.tagEncoding ;-)...
 
>> This patch interprets such a text as latin1.

Meaning that it tries to recode text from latin1 (iso-8859-1) to utf-8
(not changing gitweb output encoding, which is utf-8).

It would be much better, and much easier at least for commit message
to add --encoding=utf-8 to git-rev-list / git-log invocation.

>> Signed-off-by: Martin Koegler <[email-masked]>
>> ---
>> For correct UTF-8, the patch does not change anything.
>> 
>> If commit/blob/... is not in UTF-8, it displays the text
>> with a very high probability correct. 

It is commit (with its 'encoding' header, and `--encoding' option
we can use instead of doing it in gitweb, provided that git was
compiled with iconv support), tag (similar to commit, but IIRC
without 'encoding' header, and `--encoding' option), blob (with
no place to store encoding) and pathname in tree (which can be
different from blob encoding).

And I doubt very much about this "very high probability to be
correct".

>> As git itself is not aware of any encoding, I know no better
>> possibility to handle non UTF-8 text in gitweb.
> 
> I don't think this is a reasonable approach; I actually dispute the high
> probability - in western Europe it's obvious to assume latin1, but does
> majority of users using non-ascii characters come from there? Or rather
> from central Europe (like me, Petr Baudiš? ;-))? Somewhere else?

I also don't think that hardcoding latin1 (iso-8859-1) as default
alternate encoding is a good idea. I don't think using iso-8859-1
(outside us-ascii) is _nowadays_ that common. On the other hand I think
that not all users of koi8r, eucjp or iso-2022-jp converted (and can
convert) to utf-8; latin1 users can.

And using latin1 (other encoding) _only_ when there is an invalid utf-8
sequence is not a good idea either; I think that that there are some
latin1 sequences outside us-ascii which are valid utf-8 sequences. That
kind of magic is wrong, wrong, wrong...

> If we do something like this, we should do it properly and look at
> configured i18n.commitEncoding for the project. (But as config lookup
> may be expensive, probably do it only when we need it.)

I think it would be best to make it into %feature, overridable
or not (which would look at i18n.commitEncoding instead of at
gitweb.commitEncoding, but still a feature).

About config lookup: we can either "borrow" config reading code in Perl
from git-cvsserver, perhaps via putting it into Git.pm. Or we can
implement at last core git support for dumping whole config in
unambiguous machine parseable output: "git config --dump", e.g.
  key <LF> value <NUL>
or
  key <NUL>
(the second for "boolean" variables without set value).

Having alternate (read-only) config parser has its advantages and
disadvantages. Advantage is that we avoid fork+exec (performance),
and having two implementations is always good for having format
standarized. Disadvantage is that is yet another code to maintain,
and that config parsing (even read-only config parsing) is a bit tricky
with current git config file format.

-- 
Jakub Narebski
Poland