Re: [PATCH] Try URI quoting for embedded TAB and LF in pathnames

From: Linus Torvalds <torvalds@osdl.org>
To: Paul Eggert <eggert@CS.UCLA.EDU>
Cc: Junio C Hamano <junkio@cox.net>,
	Robert Fitzsimons <robfitz@273k.net>,
	Alex Riesen <raa.lkml@gmail.com>,
	git@vger.kernel.org, Kai Ruemmler <kai.ruemmler@gmx.net>
Subject: Re: [PATCH] Try URI quoting for embedded TAB and LF in pathnames
Date: Wed, 12 Oct 2005 14:05:25 -0700 (PDT)	[thread overview]
Message-ID: <Pine.LNX.4.64.0510121355280.15297@g5.osdl.org> (raw)
In-Reply-To: <87vf02qy79.fsf@penguin.cs.ucla.edu>

On Wed, 12 Oct 2005, Paul Eggert wrote:
> 
> Your email message suggests that we need to be cautious here.
> That message contained UTF-8 text but its header said "Content-Type:
> TEXT/PLAIN; charset=ISO-8859-1".

Well, my email message was wrong and evil, because it _mixed_ two 
different encodings in the same text. No sane client could have shown them 
both at the same time - but especially with a stupid client, you could 
have changed your terminal to show either one or the other by switching 
from utf-8 to latin1 encoding and doing a refresh.

In other words, my email really was a nasty case of not one or the other, 
but both.

Now, I believe patches can actually be that way - it's not at all 
impossible to have a diff where the _filename_ is utf-8, but the content 
of the patch itself is some byte-encoding like latin1. Or the other way 
around.

> If we're still having problems like this in 2005 then I guess we need
> to deal with them.  This suggests we should be escaping every
> non-ASCII byte, at least for patches designed to be emailed robustly.

I find that email is very robust - it's basically 8-bit clean. No 
character encoding, no crap. Just a byte stream. It really _is_ the most 
reliable format.

Now, a lot of email clients are really weak in _showing_ it, and as 
mentioned, the email that mixed both is fundamentally not something you 
really even _can_ show sanely. But who cares? What matters is not what it 
looks like, but what it _saves_ as. If you save the email message, it 
should come out as the same reliable 8-bit byte stream, or your client is 
actively corrupting messages rather than just showing them.

This is really what my argument boils down to: character set encoding 
should _not_ EVER affect the _transfer_ of the data. It doesn't matter if 
something is latin1 or utf-8, the only thing that matters is the byte 
sequence. Only when you _display_ it should you try to figure out what the 
byte sequence possibly means.

So I repeat: 
 - escape as little as possible
 - make the _viewer_ decide how to view it.

Yes, if people use "cat" to view patches, it can be dangerous. But that's 
_their_ problem.

		Linus