On 28.04.14 21:35, Jeff King wrote:
> On Mon, Apr 28, 2014 at 12:17:28PM -0700, Junio C Hamano wrote:
>
>>> 3. Convert index filenames to their precomposed form when
>>> we read the index from disk. This would be efficient,
>>> but we would have to be careful not to write the
>>> precomposed forms back out to disk.
>> I think this may be the right approach, especially if you are going
>> to do this only when core.precomposeunicode is set.
>>
>> the reasoning behind "we would have to be careful not to write"
>> part, is unclear to me, though. Don't decomposing filesystems
>> perform the manglig from the precomposed form without even being
>> asked to do so, just like a case insensitive filesystem will
>> overwrite an existing "makefile" on a request to write to
>> "Makefile"?
> Sorry, I meant "do not write the precomposed forms back out to the
> on-disk index". And by extension, do not update cache-tree and write
> them out to git trees.
>
> IOW, it is not enough to just set cache_entry->name to the normalized
> form. You'd need to store both.
>
> Since such entries are in the minority, and because cache_entry is
> already a variable-length struct, I think you could get away with
> sticking it after the "name" field, and then comparing like:
>
> const char *ce_normalized_name(struct cache_entry *ce, size_t *len)
> {
> const char *ret;
>
> /* Normal, fast path */
> if (!(ce->ce_flags & CE_NORMALIZED_NAME)) {
> len = ce_namelen(ce);
> return ce->name;
> }
>
> /* Slow path for normalized names */
> ret = ce->name + ce->namelen + 1;
> *len = strlen(name);
> return ret;
> }
>
> The strlen is probably OK since such paths are presumably in the
> minority (even for UTF-8 paths, we can avoid storing the extra copy if
> they do not need any normalization). Or we could get fancy and encode
> the length in front, but I am not sure it is worth the complexity.
>
> Anyway, the tricky part is then making sure that all cache_entry name
> comparisons use ce_normalized_name instead of ce->name.
>
> -Peff
To my knowledge repos with decomposed unicode should be rare in practice.
I only can speak for european (or latin based) or cyrillic languages myself:
- It is difficult (but not impossible) to enter decomposed unicode on the keyboard.
- Some programs under Mac OS X do not handle decomposed code points well,
an "ä" may be displayed as "¨a" for example.
- Pushing and pulling to Windows or Linux is possible, but the same problems here:
the keyboard is not prepared to enter the decomposed form, and the display may be wrong.
The only possible use case for decomposed unicode I am aware of is when you use git-bzr,
because bzr does not do the precomposition (and neither hg to my knowledge).
So for me the test case could sense, even if I think that nobody (TM) uses an old Git version
under Mac OS X which is not able to handle precomposed unicode.
Unless I have missed something.
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