Might hanging bugs remain in rsync 3.0.0?

[Tony Abernethy]

Matt McCutchen wrote:
> 
> On 7/16/07, Wayne Davison <wayned at samba.org> wrote:
> > On Sun, Jul 15, 2007 at 11:09:57PM -0400, Matt McCutchen wrote:
> > > Furthermore, from April 27 to July 10, about 2.5 months passed 
> > > without any hanging bugs being found; then, on July 11, 
> Warren Oates 
> > > reported one.
> >
> > That was a brand new one that I introduced into the code when I 
> > tweaked the index numbering in incremental mode and failed 
> to update a 
> > second section of code that interpreted the index values.  The hang 
> > bug cropped up right away in both my testing and in the 
> testing of at 
> > least one other person, and was quickly fixed.
> 
> OK, I didn't realize that.
> 
> > > This makes me worry that [...] it may nevertheless have a hanging 
> > > bug that will be found after it is released and create a serious 
> > > problem for some users.
> >
> > Such a thing is possible, but I don't think it is going to 
> be any more 
> > likely than a hang bug happening in prior versions.
> 
> It seems to me that the incremental recursion is a much more 
> dramatic change to rsync than anything else I've seen while 
> I've been working with rsync and has the potential to 
> introduce lots of obscure bugs.
> They may still all be found, but at least there are more 
> potential bugs than in previous versions.
> 
> > And the user will
> > always have the option of specifying --no-ir if they need to.
> 
> I don't like this logic; rsync should work by default.  
> Instead of making users scratch their heads when something 
> goes wrong, I think it would be prudent to make --no-ir the 
> default in rsync 3.0.0.  (I'm afraid that if you don't, some 
> distributions might.)  Users who care about the improved 
> performance and are aware of the possible consequence of 
> instability could still pass --ir.  Other users would enjoy 
> the numerous other enhancements in rsync 3.0.0 without the 
> chance of a bug in incremental recursion stopping the show.  
> Once incremental recursion has gone through a release or two 
> without any problems, I would make it the default.
> 
> Matt

I follow this list, mostly as an outsider, but a point or so
maybe worth considering.

Version jumps from 2.6.9 to 3.0.0 (not to 2.6.10 or 2.7)
You're probably ahead to start with the world-view you will
want to have after whatever dust settles. 

Rsync is not just remote copy, I sometimes use it locally
Because it is "better behaved" in odd places/situations
And if it's slower, it's not enough slower to matter.

Somehow I would expect several subtle changes in "expectations"
Of what is considered a "normal" rsync transfer.
Wild guess, but seems more likely to have a hang bug in prior
versions if there is a significant shift in expectations.