Re: [PATCH di/fast-import-deltified-tree] Windows: define S_ISUID properly

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 21, 2011, 12:07 UTC
Message-ID: <7v39fq3xpc.fsf@alter.siamese.dyndns.org>
In-Reply-To: <loom.20110921T092135-714@post.gmane.org>

Dmitry Ivankov <divanorama@gmail.com> writes:

Show 22 quoted lines

> Johannes Sixt <j.sixt <at> viscovery.net> writes:
>> 
>> From: Johannes Sixt <j6t <at> kdbg.org>
>> 
>> 8fb3ad76 (fast-import: prevent producing bad delta) introduced the first
>> use of S_ISUID. Since before this commit the value was irrelevant, we had
>> only a dummy definition in mingw.h. But beginning with this commit the
>> macro must expand to a reasonable value. Make it so.
>>  #define S_ISVTX 0
>> ...
> Ow, it's awkward that the issue was discussed in [1] but slipped and nobody 
> noticed, especially me being a patch sender.
>
> If we choose patch from [1] I'd also change a comment to smth like
> /* 
>  * We abuse the 04000 bit on directories to mean "do not delta".
>  * It is a S_ISUID bit on setuid platforms and an unused bit on
>  * non-setuid platforms supported in git. In either case git ignores
>  * the bit, so it's safe to abuse it locally.
>  */
>
> [1] http://thread.gmane.org/gmane.comp.version-control.git/179223/focus=179762

I think that the fix from Jonathan to stop abusing S_ISUID is much more preferrable; the Windows platform shouldn't have to worry about this.

And it would be even better to use a value that does not overlap with the usual bits for do-not-delta bit if possible.