Re: git on MacOSX and files with decomposed utf-8 file names

[Kevin Ballard <kevin@sb.org>]

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On Jan 21, 2008, at 4:18 PM, Theodore Tso wrote:

> On Mon, Jan 21, 2008 at 03:58:03PM -0500, Kevin Ballard wrote:
>> You're making the huge assumption that the HFS+ normalization  
>> algorithms
>> will change. As the technote states:
>>
>> "Platform algorithms tend to evolve with the Unicode standard. The  
>> HFS Plus
>> algorithms cannot evolve because such evolution would invalidate  
>> existing
>> HFS Plus volumes."
>
> Great, so even worse.  Does the tech note then specify exactly what
> version of Unicode HFS+ is using to do its "normalization"?  Or
> exactly what characters it will normalize?  After all, Unicode has
> added all sorts of characters since 1998, and I'm sure some of them
> were combining characters.
>
> And you *really* want to continue argue that a sane thing for a
> cross-platform system to do is to pervert its hash algorithm to take
> into account *one* particular OS that happened to freeze a
> normalization algorithm at some arbitrary point in time, approximately
> nine years ago?  Talk about the tail wagging the dog!!  Especially
> when you can't even justify why it was done nine years ago!

I suggest you go back and read the emails where I specifically stated  
that I'm *not* suggesting this.

>> It must have bought somebody something, or they never would have  
>> done it.
>
> Your faith in the HFS+ designers is touching.

And your arrogance is troubling. Do you really believe you are so  
smart you can claim the HFS+ designers had no reason for this decision?

>> I have no idea why HFS+ stores filenames in a normalized form, and  
>> further
>> I am smart enough to know that speculating is completely pointless. I
>> assume the authors had a good reason (which should be a safe  
>> assumption,
>> filesystem authors are a smart bunch). The reason may not be valid  
>> anymore,
>> but if it was valid back in 1998, then I can accept it without  
>> complaining.
>
> Well, I *AM* a filesystem designer (ext2/ext3/ext4), and well before
> 1998, I knew that trying to do anything with Unicode normalization was
> a fool's errand.  So if you're going to blindly trust filesystme
> designers (not something I would recommend, actually :-), trust me.
> What HFS+ is doing is dumb, dumb, dumb.

Again, I'm not saying that they necessarily did the "correct" thing,  
as I can't evaluate that without knowing their reason. I'm just saying  
there must have been a reason.

> And even if *you* can accept it, why should the git designers pervert
> any core part of git's design to support this behaviour?  Especially
> if it's legacy behaviour which will hopefully be going away, say when
> MacOS adopts ZFS --- there's an opportunity for them to start afresh,
> and not make the same mistakes they made nine years ago!

And why do you believe MacOS is going to adopt ZFS? Sure, they might,  
but assuming stuff about the future is just as bad as assuming stuff  
about the past. And git should "pervert" itself because of the simple  
fact that git has a problem on HFS+. Keeping your code "pure" is all  
well and good, except it's not particularly practical. If the git  
project has any interest in being a viable system on OS X, it really  
should behave properly. I'm sure you have various "perversions" for  
other cases.

> So why don't you suggest some kind of sane fix in the Mac specific
> code that doesn't impact any core part of git, such as its hash
> algorithm?  It would be far more productive than trying to defend a
> bad design decision made nine years ago....   :-}

How many times must I say I never suggested actually changing git's  
hashing algorithm? And if you want me to suggest a fix to git that  
works, first you have to wait for me to learn how git's internals  
work, and frankly, I have too much work on my plate right now to  
devote the time necessary to learning git's internals well enough to  
fix this problem.

-Kevin Ballard

-- 
Kevin Ballard
http://kevin.sb.org
kevin@sb.org
http://www.tildesoft.com



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