Hi all,

I was just thinking about Monticello 2 and wondering what the strategy for 
creating revisions is.

In darcs (and afaik all modern revision systems) the way it works is, I have 
a local repository and there can be any number of remote repositories.  So 
if we had one central repository called e.g. SqueakSource, after the initial 
push, my local repository is in sync with SqueakSource.  I can now make 
changes and publish them locally.  If I push these changes to the 
SqueakSource repository all the system has to do is see if the revision has 
not changed, and if it hasn't apply all my change sets to get back in sync 
and so on.

It strikes me that Squeak can do this very easily.  We already have change 
sets that actually seem very good.  So we could do the same thing; when I do 
an initial publish to the central repository I am in sync.  Now the system 
creates a new change set for all changes I do from this point forward.  
Later on when I try to sync again, if the version number has not changed the 
system need only apply the change sets I have made since the sync took 
place.  If the version number has changed, a simple conflict resolution can 
be done.

The key point here is; it looks to me like the current Monticello is 
actually scanning the whole image to find out what has changed.  This is not 
necessary as all that information and more can be retrieved via the existing 
change set mechanism.  The only change would need to be that after you 
publish to a repository, Monticello needs to rename your "current" change 
set.  If it doesn't then the next time you publish it wont see any change 
sets that aren't present in the repository and decide no work was done.  Or 
it can look if the dates are different, but then it would have to scan the 
whole change set to see what is different.  It saves processing by simply 
controlling the change set names.

Another advantage is, we can easily have the darcs ability to only apply 
certain change sets.  Using the change set tools in the image I can create 
new change sets and push different changes into those, so that if I made a 
big change I can split it up into several different change sets.  Then I 
would have the ability to say e.g. only publish the first one and the last, 
but skip the middle.

What do you all think?  Is this already what it's doing and I just didn't 
notice?  Thoughts?

Thanks,
Jason

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