[RFC] Multi-parent diffs

[Aaron Bentley]

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John Arbash Meinel wrote:
> Aaron Bentley wrote:

>> The problem is then: how to you handle the fact that the annotations are
>> different?

> I think we need to discuss annotations in general, though. As I think it
> would be reasonable to split annotations out into a separate file/cache,
> rather than storing them inline. I'm still happy that we generate them
> as we go, rather than after the fact. But most of the time when
> extracting contents, you just care about the contents, not the
> annotations. So having them mixed means you have to do extra processing
> to ignore the extra information.

That's true, though splitting them out makes our model just a bit more
complicated, e.g. one more thing that might go wrong during fetch.

But annotations, all by themselves, would be highly compressible.

> Which would also let us doing fancier things with how we store the
> delta, since it would be decoupled from the line-based annotation store.
>  Some things like making "human understandable" annotations, versus
> "optimally small" deltas, etc.

> I realize you have been thinking of other things for "line identity"
> which may effect this more, so it isn't something that I'm strictly
> advocating. As we need to evaluate the alternatives.

I think line identity is neither helped nor harmed by storing
annotations separately.  Doing line identity would mean adding a line
number to the annotation: the line number that the line had when it was
introduced.

Actually, storing annotations separately might make it easier to
associate line with a different file from the one it's currently in.
Which would make edge merging easier.

> I think 'hg' gets away with this because they don't have shared
> repositories which can mix 10 different projects in the same files.

Yes, you'd need a very good "fetch" to untangle all that.

Aaron
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