Re: [PATCH v1] convert: add support for 'encoding' attribute

From: Jeff King <peff@peff.net>
Date: Dec 18, 2017, 13:12 UTC
Message-ID: <20171218131249.GB4665@sigill.intra.peff.net>
In-Reply-To: <20171218101334.GA20685@tor.lan>

On Mon, Dec 18, 2017 at 11:13:34AM +0100, Torsten Bögershausen wrote:

> Just to confirm my missing knowledge here:
> Does this mean, that git-gui and gitk can decode/reencode
> the content of a file/blob, when the .gitattributes say so ?

That's my impression, yes.

> If yes, would it make sense to enhance the "git diff" instead ?
> "git diff --encoding" will pick up the commited encoding from
> .attributes, convert it into UTF-8, and run the diff ?

You can do something like this already:

  git config diff.utf16.textconv 'iconv -f utf16 -t utf8'
  echo file diff=utf16 >.gitattributes

I have no objection to teaching it that "encoding" means roughly the same thing, which would have two advantages:

 - we could do it in-process, which would be much faster

 - we could skip the extra config step, which is a blocker for
   server-side diffs on sites like GitHub

I don't think you'd really need "--encoding". This could just be triggered by the normal "--textconv" rules (i.e., just treat this "as if" the textconv above was configured when we see an encoding attribute).

> We actually could enhance the "git diff" output with a single
> line saying
> "Git index-encoding=cp1251"
> or so, which can be picked up by "git apply".

That extends it beyond what textconv can do (we assume that textconv patches are _just_ for human consumption, and can't be applied). And it would mean you'd potentially want to trigger it in more places. On the other hand, I don't know that we're guaranteed that a round-trip between encodings will produce a byte-wise identical result. The nice thing about piggy-backing on textconv is that it's already dealt with that problem.

-Peff