[Monotone-devel] Poll: another possible problem migrating to rosters

[Nathaniel Smith]

In monotone, it used to be possible to import two totally different
copies of a project, and then later decide to merge them, producing a
graph that looks like:
   A   B
   |   |
   C   D
    \ /
     E
i.e., E is descended from multiple graph roots.

At the moment at least, this is not possible in the roster branch,
because we've (for now, at least) left out "suturing" support.  A
similar thing used to be possible on a file-by-file basis, but this
doesn't cause a big problem, because the migration code just breaks
the link to one of the parent nodes, degrading the ancestry slightly
but preserving history overall.  However, there is a very important
node that we _can't_ do this to, which is, the "root directory" node.
The code is designed to make it possible to do wacky manipulations on
the root directory (like deleting the old one and replacing it with a
new one) in the future, but this feature is also being left out for
now.  Anyway, the upshot of all this is that the trick we use for
migrating sutured files does not work for whole sutured trees.

So, in this one particular case, there's simply no sensible new-style
ancestry graph we can map the above example to.  My question is: does
anyone have such histories out there in the wild that they will want
to migrate, and if so, can we get details on what you have now, so we
can figure out what the best solution to preserve your history will
be?

Cheers,
-- Nathaniel

-- 
Details are all that matters; God dwells there, and you never get to
see Him if you don't struggle to get them right. -- Stephen Jay Gould