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From Peter Samuelson <pe...@p12n.org>
Subject Re: Let's discuss about unicode compositions for filenames!
Date Thu, 02 Feb 2012 20:28:32 GMT

[Hiroaki Nakamura]
> Existing repositories, I think it would be better to convert them too using
> svndump/svnload. And we change svnload to convert filenames to NFC.
> However in reality we cannot force users to convert every existing repository.

Also note that if you convert a repository (via dump/load or whatever),
all working copies based on the repository are invalidated and need to
be re-checked-out.  Avoiding _that_ problem would be really hairy, I
think, very similar to the sort of work that would be needed to support
obliterate without losing working copies.

> We also need to changes servers in order to deal with existing 1.x
> clients.  We convert filenames to NFC when web_dav_svn and svnserve
> receive filenames from clients, they must first convert filenames to
> NFC.

You keep saying what we "must" do on the server side.  I propose
something that is purely on the client side.  It will solve the OS X /
non-OS X interoperability problem.  It will not solve every problem
ever faced by a Subversion user.  That's a job for 2.0.

> Yes, like I said above, "clients" actually includes components that
> run on servers like web_dav_svn, and it should read as any components
> that access to repositories and working copies.

No.  By "clients" I mean components that run on the client side.  If my
proposal had required changes to mod_dav_svn, I would not have said
"strictly client-side".  I do not propose any change to mod_dav_svn,
svnserve, svnadmin, libsvn_repos, libsvn_fs, the repository data, or
anything else on the server side.

> If you think in analogy to ASCII uppercase and lowercase examples,
> you miss the point. Please reread the Unicode Standard Annex #15
> UAX #15: Unicode Normalization Forms
> http://unicode.org/reports/tr15/

Thanks, I've read it.  The analogy stands.  We could prevent NFC/NFD
collisions as an additional service to users, something we have not
done for the past 10 years.  This would be along the lines of
preventing users from shooting themselves in the foot.

The actual _software_ problem that is solved by preventing collisions
is the same as the software problem solved by preventing upper/lower
case collisions: certain clients are unable to check out a folder that
has such collisions.  (Windows clients, in the case of upper/lower
collisions; OS X clients, in the case of NFC/NFD collisions.)

I think we are talking past each other.  You are trying to solve two
distinct but related problems: 1. OS X client-side confusion when faced
with a non-NFD repository path; 2. NFC/NFD collisions.  I am only
trying to solve problem 1.  I'm ignoring problem 2 for two reasons:

    (a) Problem 2 requires server-side work and complex compatibility /
    upgrade scenarios (dump/load, re-check-out all wcs, etc).

    (b) Problem 2 can be worked around, for new repositories (or
    repositories with no existing collisions), with a pre-commit hook.

...neither of which are true for my proposal to solve problem 1.

So long as you continue to insist that, to solve problem 1, we must
also solve problem 2, I'm pretty sure we will never come to any
agreement.

Peter

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