This comes up every time but there’s three criterion for CRDTs and git fails 2 of them. Even ignoring the requirement for automatic conflict resolution (which git can’t meet since automatic resolution fails as a matter of course) and ignoring that the conflict resolution algorithm has to be part of the data type (it’s not), it fails the requirement that separate different copies must eventually converge when brought online but that’s demonstrably false as people may use different conflict resolution mechanisms AND the commit graph of a resolved conflict may itself then be different resulting in different histories from the process of brining git online.
This is because the commit graph itself isn’t CRDT. If I commit A and then B but someone’s clone only has B applied, you can’t synchronize even automatically; different git histories don’t resolve in any way automatically at all and once you pick a solution manually your copy will not have the same history as anyone else that tries to redo your operations.
No true Scotsman doesn’t apply here because there is a very precise definition of what makes a CRDT that is a clear delineating line.
> 1. The application can update any replica independently, concurrently and without coordinating with other replicas.
> 2. An algorithm (itself part of the data type) automatically resolves any inconsistencies that might occur.
> 3. Although replicas may have different state at any particular point in time, they are guaranteed to eventually converge.
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Again, in theory it fails 2 and 3. However, in practice 3 is a normal part of working with git in a team. Barring a hard fork in git - which is equivalent to a deep copy of a CRDT. Like any deep copy of a data type, a CRDT's deep copy can be used in non-conformant manners (forks are VCS specific jargon for a CRDT deep copy; or shallow copy sometimes).
> If I commit A and then B but someone’s clone only has B applied, you can’t synchronize even automatically; different git histories don’t resolve in any way automatically
Maybe I don't understand your point specifically, but this example seems entirely solved by --rebase. In practice --rebase is typical, and best described as "do your best to automatically resolve histories; I'll handle any of the complex conflicts".
All that said, I already agreed: "academically Git is not a CRDT". However, and I'm happy to disagree with you, in practice Git is the most popular CRDT.
This is because the commit graph itself isn’t CRDT. If I commit A and then B but someone’s clone only has B applied, you can’t synchronize even automatically; different git histories don’t resolve in any way automatically at all and once you pick a solution manually your copy will not have the same history as anyone else that tries to redo your operations.
No true Scotsman doesn’t apply here because there is a very precise definition of what makes a CRDT that is a clear delineating line.