Avi Bryant wrote:
> On Wed, 23 Jul 2003, Julian Fitzell wrote:
> 
> 
>>>Well, MC already has Patch objects that it uses internally.  What I was
>>>picturing was a subclass of Version that stored a Patch instead of a
>>>complete Snapshot.  As long as you had the base version accessible, you
>>>could treat this just like any other Version - when you sent it #snapshot
>>>it would just pull in the base version and apply the patch, then hand you
>>>back the reconstructed Snapshot.  It's a space/bandwidth optimization,
>>>which is the main reason people use patches, and I think is what Daniel
>>>was asking for.
>>
>>Erm... why does it need to be a version?  And again, I think the
>>changeset is useful when you get *outside* the system, not when you're
>>inside it.
> 
> 
> We're talking at cross purposes here.
> 
> The thread started because Daniel wanted a way to send us something
> smaller than the 200k version he had produced.
> 
> My suggestion to solve that is to be able to represent a version as a base
> version ID + a patch against that base version.  This object would have
> the exact same semantics as a full version file out, but would happen to
> take up a lot less space.
> 
> So Daniel would still be sending as a "full" version, it would just be 2k
> instead of 200k.  As you say, within the system full versions (or things
> that act like full versions) are what we should be sending around.
> 
> Now, it is indeed useful to be able to produce a changeset for use outside
> the system, and I think we agree about how that should work and what it
> should or shouldn't be used for, but that's a completely separate issue.

Sure, though Daniel could also just send a generated changeset and you 
could apply that to your image and save a new version.  But whatever... 
there a few benefits to doing it your way.  It just requires more work 
on a new file format or extending the existing one.

It does seem to me though, that the tendency would then be to always 
send around smaller patches rather than full versions.  And the more you 
do that, the less likely you are to have all the versions you need to 
actually recreate a full version.  Sounds a little like a slippery slope 
towards a central repository.

Julian