What makes some version control systems better at merging?

Question

I\'ve heard that many of the distributed VCSs (git, mercurial, etc) are better at merging than traditional ones like Subversion. What does this mean? What sort of things do

Answer 1

These version control systems can do better because they have more information.

SVN pre-1.5, along with most VCS's before the latest generation, doesn't actually remember that you merged two commits anywhere. It remembers that the two branches share a common ancestor way back when they first branched off, but it doesn't know about any more recent merges that could be used as common ground.

I know nothing of SVN post 1.5 though, so maybe they've improved on this.