[darcs-devel] [issue1026] pull => bug in get_extra commuting patch (2.x)

[Jason Dagit]

Jason Dagit <dagit at codersbase.com> added the comment:

Thanks Thorkil.  I have been able to reproduce the problem locally.

It turns out to be rather interesting!

Both repositories, array and GHC, have both the patchinfos that are shown in the
new error message.  Unfortunately, the patch contents vary depending on which
repository you view those patches from.

Darcs is rightly confused here.  I mentioned this to Ian and Eric, and they
seemed to think these patches were probably created by a tailorisation of the
old GHC cvs repository into the two darcs repositories array and GHC.

Darcs has a pretty pervasive assumption that when patchinfos are equal that the
patches represent the same changes even though the patches might be in different
contexts.  

Arjan suggested that we either take it in stride or throw a catchable error up
the chain.  The former option seems dangerous to me, and the latter approach
might allow us to suggest that the user has tried to merge two very different
repositories.

Eric mentioned that there is a issue already about making patchinfos more unique
than they currently are.  I just glanced but I don't know which issue that is. 
If you find it please connect it to this issue.

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