Re: [PATCH] diff: add a config option to control orderfile

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Sep 17, 2013 at 11:14:01PM +0300, Michael S. Tsirkin wrote:
> On Tue, Sep 17, 2013 at 11:06:07AM -0700, Junio C Hamano wrote:
> > "Michael S. Tsirkin" <mst@redhat.com> writes:
> > 
> > > On Tue, Sep 17, 2013 at 10:24:19AM -0700, Junio C Hamano wrote:
> > >> "Michael S. Tsirkin" <mst@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,
> correct?
> 
> 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.
> 
> Hmm?

ENOCOFFEE

That was a silly suggestion, two identical chunks aren't that unlikely :)

> -- 
> MST