Re: [9fans] SHA-1 collision and venti

[Bakul Shah <bakul@bitblocks.com>]

On Sun, 26 Feb 2017 18:25:34 GMT Charles Forsyth <charles.forsyth@gmail.com> wrote:
>
> It's curious that svn "corrupts" the repository, if that's really what they
> mean, when two leaf files collide.
> An index or directory colliding with a file would be more understandable.

The only known collision is for files. I suspect this was seen
as a "can't happen" event so may be dealing with the error was
not done right. You can read the report:
https://bugs.webkit.org/show_bug.cgi?id=168774

> > Venti detects a collision on the attempt to write the second copy if that
> > differs from the earlier one stored (error "store collision"). The earlier
> > copy is untouched (venti anyway is write-once per score).

Good to know at least it /detects/ score collisions.

The concern would be that one of two colliding files *can't*
be archived and it will be lost.  We only have one example
so it is not a big deal right now.

> > Fossil doesn't handle it well, because it turns up during archiving and
> > ends up marking the archive attempt as failed, but it will try again.
> > Meanwhile, you've got time to change fossil to check the venti error
> > return for "score collision" and announce it, loudly, discarding the second
> > one.

Hopefully the two versions can co-exist on fossil?

> > Obviously if you care about something, make sure your version is in venti
> > first! Chances are that collisions arise from naughty people tricking you
> > later. Probably.

Or may be you are doing research on collsions?!