Subject: Breaking rdiff-backup and btar (was Re: [bug#30448] Update librsync to 2.0.1)

From: Leo Famulari <[email-masked]>
Date: Tue, 24 Apr 2018 13:57:15 -0400

On Mon, Apr 23, 2018 at 02:58:17PM +0200, Ludovic Courtès wrote:
> [email-masked] (Ludovic Courtès) skribis:
> 
> > Leo Famulari <[email-masked]> skribis:
> >
> >> Is anyone using one of the dependent packages interested in looking more
> >> closely at this?
> >
> > I’m not using it, but at first sight the patch LGTM.
> 
> Ping!  :-)

My understanding is this update will break btar and rdiff-backup.

I suspect this will annoy some Guix users. Plus, I don't know if these
projects make an effort to detect MD4 collisions or not; perhaps they
are safe to use despite the broken librsync dependency.

We could add an old librsync package variant for those packages, but we
should add a note about the reliance on MD4.

I'll wait a few days for more feedback.

PS — this issue highlighted for me that the duplicity backup program
also depends on librsync with MD4. For recent versions of librsync,
duplicity forces librsync to fallback to MD4...