On Tue, Sep 17, 2013 at 11:06:07AM -0700, Junio C Hamano wrote:
> "Michael S. Tsirkin" <m...@redhat.com> writes:
> > On Tue, Sep 17, 2013 at 10:24:19AM -0700, Junio C Hamano wrote:
> >> "Michael S. Tsirkin" <m...@redhat.com> writes:
> >> 
> >> > So might it not be useful to tweak patch id to
> >> > sort the diff, making it a bit more stable?
> >> 
> >> That is one thing that needs to be done, I think.  But it would be
> >> unfortunate if we have to do that unconditionally, though, as we may
> >> be "buffering" many hundred kilobytes of patch text in core.  If we
> >> can do so without regressing the streaming performance for the most
> >> common case of not using the orderfile on the generating side (hence
> >> not having to sort on the receiving end), it would be ideal.  I am
> >> not sure offhand how much code damage we are talking about, though.
> >
> > So make it conditional on the presence of the orderefile option?
> That would mean that those who set orderfile from configuration in
> the future will have to always suffer, I would think.  Is that
> acceptable?  I dunno.
> Also, if the sender used a non-standard order, the recipient does
> not know what order the patch was generated, and the recipient does
> not use a custom orderfile, what should happen?  I thought your idea
> was to normalize by using some canonical order that is not affected
> by the orderfile to make sure patch-id stays stable, so I would
> imagine that such a recipient who does not have orderfile specified
> still needs to sort before hashing, no?

Thinking about it some more, it's a best effort thing anyway,

So how about, instead of doing a hash over the whole input,
we hash each chunk and XOR them together?

This way it will be stable against chunk reordering, and
no need to keep patch in memory.


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