Please check my thinking on bug 646979

[James Westby]

On Mon, 04 Oct 2010 19:20:32 -0500, John Arbash Meinel <john at arbash-meinel.com> wrote:
> So you preserve the content of exactly D or E, you just generate a new
> node in the graph to supersede the other one, correct?

Yes.

> Say D is the 'winner', then you end up with a patch that reverts
> everything in E.

Yes, except that D should in fact contain all the changes of E, so it's
not like we are completely backing them out, but that's how it appears
in the revision graph.

> In the below graph, the content in H == D, so when generating I, we
> should see D as the common base, and I would then == F (because H - D ==
> NULL, so there is nothing to apply to F to generate I)

Yes.

> Going further with the above example, it really depends on what you
> want. From what you've stated about "whichever one wins", then you sort
> of simplify what you want. You explicitly stated that you are rejecting
> any of the 2.1 changes that weren't in 3.0. I'm having a bit of a hard
> time figuring out what you are trying to preserve in G, versus just
> telling it "and now you are F/I".

We want to preserve any changes vs. E. G has some packaging changes
v.s. E, at least a Debian directory, and we want to preserve them,
conflicting where the other side has made incompatible changes. That's
again rather simplifying things though.

> Probably. Examples can certainly shed light on confusing points.

If you grab r44 of lp:ubuntu/lucid/brltty and r14 of
lp:debian/sid/brltty then you can merge-package them to see an instance
of this issue.

Thanks,

James