Re: [PATCH] Teach "git add" and friends to be paranoid

[Junio C Hamano <gitster@pobox.com>]

Nicolas Pitre <nico@fluxnic.net> writes:

>> Honesty is very good.  An alternative implementation that does not hurt
>> performance as much as the "paranoia" would, and checks "the input well
>> enough" would be very welcome.
>
> Can't we rely on the mtime of the source file?  Sample it before 
> starting hashing it, then make sure it didn't change when done.

I suspect that opening to mmap(2), hashing once to compute the object
name, and deflating it to write it out, will all happen within the same
second, unless you are talking about a really huge file, or you started at
very near a second boundary.

I am perfectly Ok that it will have false negatives that way, but if the
probability of it catching problems is too low because git is too fast
relative to the file timestamp granularity, then it doesn't sound very
useful in practice, unless of course you are on better filesystems.

It won't have false positives and that is a very good thing, though.