> If there's a bugfix, I say "Get me that bugfix patch". [..] It always just works.
> Darcs almost always gets merges correct, or it fails to do the merge at all.
One of these is not like the other, which IMO is the problem with "magical" merging systems. Great when they work, f*cking hell nightmare when they don't.
I'd rather have something like git that works in normal usage all the time, and when it fails, is easy to fix. YMMV.
If you try to analyse merge systems mathematically, git's merge system is the "magical" one. It is just a heuristic algorithm, with no solid property you can rely on.
In contrast, Darcs and Pijul's merge are associative, and Pijul's merge is commutative. Even if you don't like maths, this means that they will always behave deterministically. This also means you can use them in scripts, although darcs might sometimes have performance problems (pretty bad ones, actually).
FWIW, this is traditionally quite possible with Darcs. I sort of misformulated in my original post; it's not like it just gives up and you're at square one. The workflow IIRC was basically the same as Git: it'll throw its hands up and you make a new commit to fix everything. So that isn't really a problem or any different. Note that Darcs 1 did have the exponential merge case on top of this, however, which was pretty unfortunate (and really a byproduct of the design of the change format, among other things).
In all honesty, given years of experience with Git, and fondly using Darcs as my first version control system: I still think merges are absolutely the one thing it beats Git at, hands down. When it works and it does its job, it always is correct. When it doesn't, you can bail it out. Not much different, but the "always is correct" and dependencies-being-implicit is what makes it good. Darcs could have saved me at least dozens of hours of hair pulling when doing STABLE merges I estimate... Git's still good. I wish it could do that, though...
Your note about git is interesting. In fact, Git is, in at least some cases, more magical than other VCSs in the merge department. You might just not be aware of it due to being so familiar. When I say "Darcs always gets the merge correct", I don't just mean it literally finishes with exit code 0, but also that the semantic model is, in some sense, more 'correct' or 'intuitive':
Darcs (and others) always get this 'merge associativity' case correct, where 'Base+A+B' where (+) is merge is associative (so it doesn't matter how you 'bundle' the changes or whatever). That means you have less edges to worry about. And to be fair, I don't think there's anything inherent about Git where this particular case can't be fixed. It's just a good example of why people are trying projects like Pijul/Darcs at all, so these things can be formalized and understood. The theory of patches is actually rather rich and helps formalize a lot of these notions of what a "merge" really is in an algebraic sense, how patches relate to one another, etc.
> Darcs almost always gets merges correct, or it fails to do the merge at all.
One of these is not like the other, which IMO is the problem with "magical" merging systems. Great when they work, f*cking hell nightmare when they don't.
I'd rather have something like git that works in normal usage all the time, and when it fails, is easy to fix. YMMV.