Use dominator for common ancestor? Weave merge?

[Jan Hudec]

On Tue, Feb 07, 2006 at 12:50:14 -0500, Aaron Bentley wrote:
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> A problem that can occur with DVCS is criss-cross merges.  These were a
> source of much excitement on the Gnu Arch development list.  We have
> already encountered some criss-cross situations in bzr development, and
> I think the problem will only increase now that we have three
> integration branches.
> 
> (for more discussion of criss-cross merges, see
> http://revctrl.org/CrissCrossMerge)
>
> [...]
> 
> So:
> 1. Does anyone disagree with this analysis?

No. It's correct.

However, the abovementioned page says about the dominator approach that 'it
has it's own problem'. The only known, or at least known to any contributor
to revctl.org, algorithm that can handle criss-cross merge sanely is weave
merge.

> 2. Does anyone feel like implementing dominator detection?
> 
> Additionally, weave merge should handle criss-cross merge better than
> three-way.  We still need a base to perform non-text merges, however.
> 
> 3. Should we make weave merge the default?

Yes. It will be needed for cherry-picking too.

> 4. Should we make weave merge dump BASE as well as THIS and OTHER?

The problem is it does not really have a base. Perhaps it could attempt to
construct some kind of base annotation. It might be something like merge of
all maximal common ancestors.

> 5. Does anyone feel like reimplementing --reprocess to support weave merge?
> 
> Aaron

-- 
						 Jan 'Bulb' Hudec <bulb at ucw.cz>
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