As discussed on IRC earlier, The combination of the directory diffing
code producing broken trees, and the Darcs.Patch.Prim.mapPrimFL
"optimisation" fixing them, is broken:

$ darcs --version
2.4.3 (release)
$ darcs init
$ mkdir foo
$ touch foo/foofile
$ darcs rec -l -a -m "foo patch"
Finished recording patch 'foo patch' 
$ mkdir bar
$ touch bar/barfile
$ rm -r foo
$ darcs rec -l -a -m "bar patch"

darcs failed:  Error creating file ./bar/barfile
$

The discussion starts somewhere around here:
  http://irclog.perlgeek.de/darcs/2010-08-09#i_2682484

Search for mapPrimFL.

It seems to be confirmed by Ganesh if you read the log.

Adding Ganesh as he was participating in the discussion and seems to 
know what's up.

I've pushed the test to HEAD.  It does seem to be not so good that Darcs 
complains about an inconsistent repo when you try to record a patch (I'm 
assuming Ian cut off that the complaint).  

I've also checked that this test fails on HEAD and darcs 2.4.3, but 
passes on darcs 1.0.9 and 2.3.1.  So this issue appears to be a 
regression from the 2.3 line.

Perhaps 2.8.0 is a reasonable milestone for this bug (at least?)

This bug is marked need-action, but the action needed was not specified.     
That said, I think we've run out of easily identifiable actions (write 
test, check for regression) and we're stuck with "determine cause for 
this bug".  But since we know what we're regressed again, this should be 
fairly straightforward?  If so, this bug needs to move to need-
implementation.

Sorry Reinier, another 2.5 blocker for you!  

Ian says the fix is known and wouldn't take very long.  His statement of 
the fix is "Make the tree diffing code return valid patches".  I'm going 
to assume that's sufficiently specified for a need-implementation.  Who 
can fix this?  Please volunteer.

Updates: the inconsistent repo complaint only occurs with old fashioned 
repositories.  Sorry for the lazy assumption, Ian

The following patch updated issue issue1913 with status=resolved;resolvedin=2.8.0 HEAD

* resolve issue1913: sort changes in treeDiff 
Ignore-this: 3693df699c664a8f47dc0e0f974c9b7d

The following patch updated issue issue1913 with status=resolved;resolvedin=2.5.0 CURRENT

* resolve issue1913: sort changes in treeDiff 
Ignore-this: 3693df699c664a8f47dc0e0f974c9b7d