[darcs-users] darcs error: "cannot handle mergers" ??

Eric Kow kowey at darcs.net
Fri Mar 13 10:10:53 UTC 2009

Hi Steven,

On Thu, Mar 12, 2009 at 22:40:03 -0400, Steven G. Johnson wrote:
> Darcs has started giving me the following error when I run almost any  
> command (even "darcs repair") on my repository:
> 	darcs: Cannot handle mergers other than version 0.0
> 	0.1
> 	Please use darcs optimize --modernize with an older darcs

Wow! Looks like you've got a repository from the early days.

> Any ideas on how this could occur?

I believe that the short answer is darcs 2.

We would have to dig into the code to find out for sure, but from my
somewhat fuzzy memories of reading the darcs code and my re-reading of
early in darcs history, David worked on different versions of the
'merger' algorithm (for conflicts) before settling one which stayed with
darcs for a very long time.  The algorithm to use was marked in the
patches directly.  Your repository was around from when darcs was still
using one of the old merger algorithms.  Anyway the work for darcs 2
involved rearranging the code a bit, and I think removing support for
older merger algorithms (in place of this advice).  This story may be
incorrect, but it is what I think happened.

> The suggested fix, using an "older darcs" to run "darcs optimize  
> --modernize" is a little obscure.  What version of Darcs do I need?  
> Currently I have 2.0.2.

I did a darcs help optimize with darcs 1.0.9 and found that it has a
--modernize-patches option.  Could you try that?  Needless to say, it
may be good to create a tarball of the original repository before
optimizing it.

If you could put these online, it would be great! (as an example to us
for the kinds of repositories we should try to keep in mind)

> I should also note that the darcs.net page has no download links for 
> older versions, although I was able to do it by guessing the URL.

Old releases are on <http://wiki.darcs.net/index.html/OldReleases>
(we've only just created that page yesterday! nice coincidence),
this page being linked from <http://wiki.darcs.net/index.html/Binaries>

I hope this helps!  Please let us know how you get on.

Eric Kow <http://www.nltg.brighton.ac.uk/home/Eric.Kow>
PGP Key ID: 08AC04F9
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