Re: icase pathspec magic support in ls-tree

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Oct 2, 2022, 19:07 UTC
Message-ID: <YznhYzWztkPc9pJk@tapette.crustytoothpaste.net>
In-Reply-To: <220930.86r0ztufwd.gmgdl@evledraar.gmail.com>

On 2022-09-30 at 13:53:16, Ævar Arnfjörð Bjarmason wrote:

Show 5 quoted lines

> You might find ASCII-only sufficient, but note that even if you get this
> working you won't catch the more complex Unicode normalization rules
> various filesystems perform, see the fsck code we carefully crafted to
> make sure we don't get something those FS's will mistake for a ".git"
> directory in-tree.

What's even worse is that different OSes case-fold differently and the behaviour differs based on the version of the OS that formatted the file system (which is of course not exposed to userspace), so in general it's impossible to know exactly how case folding works on a particular system.

It might be possible to implement some general rules that are overzealous (in that they will catch patterns that will case-fold on _some_ system), but in general this is very difficult. The rules will also almost certainly change with newer versions of Unicode.

I'll also point out that there is no locale-independent way to correctly case-fold Unicode text. Correct case-folding is sensitive to the language, script, and region.

-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA