From mboxrd@z Thu Jan  1 00:00:00 1970
From: Junio C Hamano <junkio@cox.net>
Subject: Re: heads-up: git-index-pack in "next" is broken
Date: Tue, 17 Oct 2006 21:16:26 -0700
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To: Nicolas Pitre <nico@cam.org>
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	message of "Tue, 17 Oct 2006 22:23:30 -0400 (EDT)")
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Nicolas Pitre <nico@cam.org> writes:

>> but if somebody did so then it would mean a disaster to have an 
>> accidental collision of an 8-byte offset value plus 12-byte traiing 
>> NUL and another base object whose object name happens to match that 
>> pattern.
>
> Not really.  The only effect that would have on the sorted list of 
> delta entries -- such sorting used to bring all deltas with the same 
> base object contigously -- is that those deltas might not be perfectly 
> contigous wrt their base object.  This is why there is a test to skip 
> deltas if they happen not to be of the expected type.

Ah, I misread the code that uses union actually checks the type
in struct delta_entry (which embeds the union).  There won't be
any collision problem and you support both types at the same
time just fine.

And your patch to compare only the first 20-bytes makes sense
(assuming ulong is always shorter than 20-bytes which I think is
safe to assume).