Mutating history in Subversion and Bazaar

[John Arbash Meinel]

David Allouche wrote:
> Aaron Bentley wrote:
>> John Arbash Meinel wrote:
>>>> Unfortunately we don't. We check the sha-1 sums when we extract
>>>> the texts, but to check them at 'join()' time means that we have
>>>> to extract the content, apply it to the previous text in the case
>>>> it is a delta, which may mean extracting all of the other
>>>> previous texts, etc.
>> Yes.  I suggested we check the parent sha-1's because it's cheaper to
>> do that.  It provides a good guarantee against history mutation, but
>> it doesn't provide a good guarantee against broken knit deltas.
> 
> What Aaron says.
> 
> I think that would be a sufficiently useful safeguard against the sort
> of history mutation problems you find in all reproducible import
> systems, like the foreign-vcs plugins.
> 
> Can we get that implemented before 1.0? Please?
> 

...

> To check for history mutation, we also need to be able to check multiple
> repositories for agreement, in addition to internal consistency. Maybe
> the UI for that could be "bzr check [branch] ..." (note the ellipsis).
> 
> Can that be a 1.0 goal too?
> 

Both seem worthwhile for an 1.0 release. I was thinking to try and get
the consistency checking while merging into a 0.11 release if I have
enough time. I think it is very worthwhile to do integrity checking as
you go. But we'll have to see the performance impact.

John
=:->

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